Cable Tray Sizing Calculator

Containment self-weights: Legrand Swifts, Unitrunk Speedway, Cablofil catalogues. Cleats: Ellis Patents datasheets (Vulcan+ DS03E iss. 06, Atlas DS13E iss. 03, Emperor 07/2026). Cables: 143 in the shared store, from Prysmian and supplier datasheets. SWA to BS 5467 from the Eland Cables dimensions tables, with the 5-core 70 and 95mm² sizes from the Cleveland Cable BS 5467 datasheet (the Eland table stops at 50mm²). Singles: 6491X PVC and 6491B LSZH, 15 sizes each from 2.5 to 300mm², from the Cleveland Cable datasheets. Cat 6A from Brand-Rex and Leviton datasheets, AV and control from Belden technical data. Rod capacities: BS 8519:2020 Table E.2.

11/10/2026 (PD Cable Database 1.0.2): 24 FP400 cables have Prysmian's current figures: larger diameters for 3-core 1.5 to 16 and 35, 4-core 1.5 to 35 and 240 mm², smaller for 3-core 70, 4-core 70 to 185, 300 and 400 mm². Width, tray count, bracket load, drop rod and Grouping factor (Cg) can change; a chosen width or 45% trunking space factor can now be exceeded, or no longer exceeded. On-Site Guide Table D1 now applies to 4-core 70 mm², with wider spacings for 3-core 2.5 and 4-core 6 mm². Re-check FP400 runs: reopened saved reports have the new figures and no note of the change. 11/10/2026 (PD Cable Database 1.0.1): the eight aluminium wire armoured (AWA) cables have Eland Cables' 0.6/1 kV figures, not 1.9/3.3 kV. From 150 mm² up, diameters are 1.1 to 4.2 mm larger: runs can need one size wider or one more tray. AWA-120-1c is 0.8 mm smaller: runs can need one size narrower or one tray fewer. Weights are 7% to 22% lower; bracket load, drop rod and Grouping factor (Cg) can rise or fall. AWA-400-1c and AWA-500-1c are now beyond On-Site Guide Table D1. Re-check AWA runs sized before this release: reopened saved reports have the new figures and no note of the change. 08/10/2026 (2.16.0): the drawing headings read CROSS-SECTION, SECTION and LOADS; the sheet titles read CROSS-SECTION and SECTION. At any spare, including the default 25%, re-check these, which can be wider: medium and heavy duty trays with under 15 mm of width free; trefoil runs with spacing and two single cores left over; and split runs, where a tray could be narrower than its cables. Medium duty trays with 21 to 30 mm cables can be one size smaller, or one tray fewer. With more or fewer trays, a run's Grouping factor (Cg) can change. The cables' kg/m and Reference Method are unchanged. 08/10/2026 (2.15.0): single layer basket runs use wire mesh tray grouping factors, not perforated tray: most rise, three fall by 0.01 (two per basket). No factor is printed for more trays than Table 4C4 or 4C5 lists. Medium duty tray flanges are drawn inwards: with no spare, the tray can be one size larger, and heavier, where cables over 21 mm would sit under them. Re-check these cases. Ladder and basket callouts no longer say "return flanges". The drop-rod loading card is beside the Bracket loading drawing on wide windows. The grouping line's missing space is fixed. Otherwise the calculations are unchanged. 01/10/2026 (2.14.0): the Bracket elevation is now called Bracket loading. Grouping factors are no longer printed beyond the limits of BS 7671 Table 4C4 (more than 6 cables per tray when spaced, or more than 9 on two or more trays) or Table 4C5 (more than 3 three-phase circuits per tray). A line names the limit and Table 4C1 NOTE 7. The factor printed for these runs before 2.14.0 overstates current-carrying capacity: re-check cables sized with it. In 2.13.1, the screening room bracket's printed Cross-section showed rod B's size and "minimum" on separate lines; this is fixed. Otherwise the calculations are unchanged. 01/10/2026 (2.13.1): on the drawing sheets, in the tool and in print, the Notes heading now has more space above it: about 5.4 mm in print (it was 0.4 to 3.4 mm). In 2.13.0, the Notes, Abbreviations and Key column overlapped the Drawing data heading on the printed Cross-section sheet of the screening room bracket with 8 or 10 runs. It is now drawn 10 mm wider in print where it would not fit above the Drawing data. The pictures in the exports show the same changes. The calculations and wording are unchanged in the tool, the printed report and the exports. 30/09/2026 (2.13.0): the Bracket elevation is now a drawing sheet, like the cross-section. It shows where each load acts and, in the Engineering Toolkit, the run loads, rod loads and minimum drop rod size. Before any cable is entered, a drawing marked SAMPLE is shown and kept out of the result, report and exports. In the Toolkit, both sheets can print at the end of the report, each on its own A4 landscape page, and appear in the Word and Excel exports. The pictures in an export made straight after a change now show the changed arrangement. The calculations are unchanged. 30/09/2026 (2.12.0): the cross-section drawing is now a drawing sheet with callouts, notes, abbreviations and a key. In the Engineering Toolkit, with "Include the cross-section drawing in the report" ticked, the drawing prints on its own A4 landscape page with a run schedule. The Word and Excel exports include a picture of that page. The Specialist lighting lines now name the Lighting, General power and Lighting & power services. The calculations are unchanged. In an automated check of 34 brackets, each drawn on a wide screen, a phone and the printed sheet, no text overlapped or ran outside the sheet frame. 30/09/2026 (2.11.0): the cable list was moved to PD Cable Database, a separate plugin on projectdesign.io. The cables in the list, the calculations, the wording shown in the tool, the drawings, the printed report and the exports are unchanged. The same list is used, as before, in the Cable Duct, Conduit and Trunking tools, which are not changed in this release. In an automated check, the cable list in 2.11.0 was identical, byte for byte, to the list in use before this release (143 cables, read on 30/09/2026), whether PD Cable Database was active or not. 30/09/2026 (2.10.1): a run of loaded circuits laid Bunched is now sized on its single layer width, so its tray can be wider or narrower: re-check trays sized before 2.10.1. Specialist lighting no longer counts as a loaded tier, so other runs on the same bracket can be given a grouping factor up to 0.06 higher, or one where none was printed because of the tier spacing, but no factor above 20 circuits on one tier. A cable not in the cable list is now kept as a Custom cable and named in a check line. Otherwise the calculations are unchanged. 30/09/2026 (2.10.1): the screening room example now has 100 x 50 mm trunking on RUN 2, not 150 x 100 mm, so its total per bracket is 21.18 kg, not 23.53 kg. 29/09/2026 (2.10.0): you can now duplicate a run, move a cable between runs and choose the service "Life safety supply". Above 20 circuits, a single layer on one tray is now given no grouping factor, as BS 7671 Table 4C1 gives none. Seven FP600 cables now match the current Prysmian FP600s datasheet. Otherwise the calculations are unchanged. The loading basis now defaults to "Not subject to simultaneous overload"; the grouping factor is unchanged. The containment is drawn 100 mm from the wall by default. Abbreviations are now written out. Re-check cables sized before 2.9.2 on a run of loaded circuits laid Bunched. 26/09/2026 (2.9.3): in the Engineering Toolkit, the printed report now includes the Sizing basis section, which it had not printed before, and again gives the SWL each run is checked against. A printed section is no longer located by its title, so rewording a title cannot leave it empty. No calculated value changed. In the printed report and the exports, each run's support system line now gives its total load and names all tiers of a stacked run. The Cross-section drawing and its caption no longer show cable ladder when a cable over 50 mm across is on tray or basket. A References entry for BS 7671:2018+A4:2026 Table 4C1 item 1 was added, and the wording of ten other lines in the tool and the report was corrected. The green for a pass, the amber for a point to check or a warning, and the grey for a neutral mark are now darker, so that any white text on them meets the 4.5:1 contrast that the Web Content Accessibility Guidelines 2.2 require at level AA for text of 12 px; this change applies only to the colours, not to any calculation, result, wording or layout. Apart from these changes, the calculations, the wording shown in the tool, the drawings, the printed report and the exports are unchanged. A new automated check prints 14 arrangements and finds in each printed report every result, check line, factor and sizing step shown in the tool, 1,031 items in all, as whole words at 7 pt or more; it fails on a copy of 2.9.2 with the title of the grouping section changed. The new check, a check of the colours and the header bar, the Table 4C1 item 1 check, the 2,553-bracket enumeration, the 27 random brackets, the 56 hand-calculated checks, the printed report layout check (eight cases) and the audit checks were run on the final build with no finding; the served files matched the release and the page was read. 26/09/2026 (2.9.2): a run of loaded circuits with its Lay set to Bunched is now given the grouping factor of BS 7671:2018+A4:2026 Table 4C1 item 1 for the circuits in its bunch. In 2.9.1 it was given a single layer factor, or none. For example, 4 multicore cables bunched on one perforated tray are now given 0.65, not 0.77. Above 20 circuits in a bunch no factor is printed. In the Engineering Toolkit, the grouping panel and the printed report also state the single layer factor of the same cables, except on unperforated tray or where the tier spacing is under 300 mm or not entered. Twelve lines citing a standard were corrected: none now says "must", and a line says "should" or "shall" only where the clause it cites does. Apart from these changes, the calculations, the wording shown in the tool, the drawings, the printed report and the exports are unchanged. A new automated check tests bunched runs of every loaded service on tray, basket and ladder against Table 4C1 item 1, at circuit counts across the table and above 20, and fails on the 2.9.1 build. A check compared 2.9.1 and 2.9.2 on 38 arrangements and found only the corrected lines. The new check, the 2,553-bracket enumeration, the 27 random brackets, the 56 hand-calculated checks, the printed report check (eight cases) and the audit checks were run on the final build with no finding; the served files matched the release and the page was read. 26/09/2026 (2.9.1): the simultaneous overload line, the perforated tray definition, the drawing caption of a bunched run and four other lines were corrected. The drawings now have the PD Power Distribution tool's colours and font, and the printed report has the same colours. A guidance pop-out no longer blocks the controls it covers, and on a touch screen it shows only while you are in its field. Apart from these changes, the calculations, the wording shown in the tool, the drawings, the printed report and the exports are unchanged. A new check compared the drawings, the printed report and the report data of 2.9.0 and 2.9.1 on 32 arrangements and found only the colour and font changes and the corrected lines. In the review of 2.9.0, 41 controls were used at desktop and phone width in the free and Engineering Toolkit versions, and every line shown was read against its source. The 2,553-bracket enumeration, the 27 random brackets, the 56 hand-calculated checks, the printed report check (eight cases) and the audit checks were re-run on the final build with no difference; the served files matched the release and the page was read. 26/09/2026 (2.9.0): apart from the save and export panel, the panels, buttons and input boxes now have the PD Power Distribution tool's colours and font. The tool name, version and Start again button are now in a dark header bar. On a phone 375 px wide the page no longer scrolls sideways. This was checked with all seven typical arrangements in the Engineering Toolkit version and four in the free version. The program file for the calculations, check lines, drawings, printed report and exports is byte for byte the 2.8.3 file, so the 2,553-bracket enumeration was not re-run. A new automated check reads the colours, font, header bar and drawing tabs at desktop and phone widths, and fails on the 2.8.3 build. The printed report check was re-run on its eight cases with no finding, and each matches its 2.8.3 print page for page. The automated check of the fire alarm note, the automated check built for 2.7.3, the audit checks, the 27 random brackets and the 56 hand-calculated checks were re-run on the final build with no difference. The wording shown in the tool is unchanged apart from the header bar, and every control works as before; the served files matched the release and the page was read. 24/09/2026 (2.8.3): the note citing BS 5839-1:2025 35.5 is now shown for fire alarm cables only. The owner found it in the live tool for an FP600 power cable on a General power run. On 2.8.2 every cable type beginning FP (FP200, FP400, FP500 and FP600) was treated as a fire alarm cable for this note, and where such a cable shared a run with other cables the note stated 'move them to a run of their own, or add a dedicated partition' on cable tray, ladder and basket as well as on trunking. Clause 35.5 was read in the standard, and it applies to conduit and trunking only. The owner ruled the same day which cables the note is for: every fire-resistant cable on a Fire alarm run, and FP200 on any other run except a life safety run, where BS 8519 is applied as before. FP400 and FP600 are power cables and FP500 is treated as a life safety cable. On trunking the note now states the clause's recommendation, a compartment reserved solely for the fire alarm cables; on cable tray, ladder or basket it states that there is no requirement in the clause for a separate run, and that a run of their own is good practice. The References line in the report now also states the scope of the clause, and the words 'as arranged here' were removed from its last sentence because they were not true where cables share a run. A new automated check built 1,440 brackets on 2.8.2 and on 2.8.3, 720 in the free version and 720 in the Engineering Toolkit version, for all 12 services, all six containment types and ten sets of cables. On 2.8.3 every note matched the clause and the owner's ruling, and apart from this note and the References line nothing changed in the wording shown in the tool, the drawing, the printed report or the report data; the same check fails on the 2.8.2 build. The duct, conduit and trunking tools were checked for the same fault and do not have it. The 2,553-bracket enumeration, the 27 random brackets, the printed report check and the audit checks were re-run on the final build with no difference; the calculations are unchanged; the served files matched the release and the page was read. 24/09/2026 (2.8.2): one cable was added to the cable list, FP600S 5-core 35 mm², with an overall diameter of 39 mm and a weight of 3,300 kg/km from the current Prysmian FP600s datasheet. The same datasheet gives the figures already in the list for the 3-core and 4-core 35 mm² cables, so the new cable follows that edition; the 2014 copy, which gives 37 mm and 3,100 kg/km, was not used. The list is shared, so the cable also appears in the duct and conduit tools. Calculated by hand with 25% spare, one of these cables needs a 50 mm tray and weighs 4.13 kg/m, and four need a 225 mm tray at 16.5 kg/m; the tool gives the same figures. The 2,553-bracket enumeration, the 27 random brackets, the printed report check and the audit checks were re-run on the final build with no difference. The figures for every other cable, the wording shown in the tool, the printed report and the exports are unchanged. After upload, the served files matched the release, and the cable list on the site holds the new cable with these figures, 143 cables in all. 18/09/2026 (2.8.1): a sample was added to the list of typical arrangements, a dedicated life safety bracket for the primary supply with FP600 power cables on a heavy-duty ladder and FP500 control cables on a tray above it; the secondary supply is left for a separate route (BS 8519:2020 7.1). BS 8519 is applied when the sample is chosen and every check on it is a pass. The owner ruled the same day that a fire alarm or emergency lighting run beside a life safety run does not raise the 7.3 line, because those installations are subject to BS 5839-1 and BS 5266-1; the tool already worked that way and did not change. The printed report check now prints the sample as well, and once more with its second run changed to the secondary supply, eight cases in all, and measured the text size, page use, repeated sentences and page numbers with no finding. The automated check of the life safety services, the 2,553-bracket enumeration, the 27 random brackets, the 56 hand-calculated checks and the audit checks were re-run on the final build with no difference; the calculations, the wording shown in the tool, the printed report and the exports are unchanged; the served files matched the release and the page was read. 18/09/2026 (2.8.0): two services were added to the Service list on a run, Life safety, primary supply and Life safety, secondary supply, for the supplies to life safety and fire-fighting equipment; BS 8519:2020 6.1 recommends a secondary power supply independent of the primary supply. BS 8519 is applied to the bracket when either service is chosen and stays applied while a run serves life safety. The tool now states when the primary and the secondary supplies share one bracket (7.1, diverse cable routes), when life safety cables share a bracket with other services (7.3, a dedicated cable support system) and, for Engineering Toolkit users, when a cable on a life safety run is not a fire-resistant type (clause 11); each line reads the same in the tool, in the printed report and in the report data. Every clause quoted was read in BS 8519:2020, and a new automated check reads them again from the standard on every run. The same check built 144 brackets on 2.7.8 and on 2.8.0, for every earlier service with BS 8519 off and at each category, and found no difference in the wording shown in the tool, the drawing, the printed report or the report data; it compared the figures of a life safety run with those of an Other run on 162 brackets and found them equal, and it fails on the 2.7.8 build. The 2,553-bracket enumeration, the 27 random brackets, the 56 hand-calculated checks, the printed report check and the audit checks were re-run on the final build with no difference; no width, load, reaction or rod value changed for any earlier service; the served files matched the release and the page was read. 16/09/2026 (2.7.8): the wording in the tool was revised in plain UK English. The Engineering Toolkit lines and the cable weight tip now say in the tool, and the segregation checks are called checks. The calculations, the printed report and the exports are unchanged. The printed report check on all six presets, the audit checks, the 27 random brackets, the 56 hand-calculated checks and the 2,553-bracket enumeration were re-run on the final build with no difference; the served files matched the release and the page was read. 15/09/2026 (2.7.7): the printed report was rearranged to read as a technical report, after the owner's review of a printed 2.7.6 report. The bracket drawing now prints large enough to read: text on the report is 8 pt or larger and the drawing labels 6.8 pt or larger, where some labels printed at 3 to 4 pt on 2.7.6. One summary line names each run that needs action, the run schedule shows a size check and a load check for every run, the basis of the load check is stated once instead of on every run, and a findings table lists the runs that need action and the fire-resistant cable lines. Columns with no entries are left out, the sections after page 1 no longer start on a new page, and every page shows its page number. A new automated check prints the report to PDF for every preset and measures the text size, nearly empty pages, repeated sentences, empty columns and page numbers; it fails on the 2.7.6 build. A second check compared the wording and the drawing in the tool and the report data on 2.7.6 and 2.7.7 and found no difference; the 2,553-bracket enumeration, the 27 random brackets, the 56 hand-calculated checks and the audit checks were re-run on the final build with no difference; no width, load, reaction or rod value changed; the served files matched the release and the page was read. 15/09/2026 (2.7.6): the notes written inside the program code were rewritten in plain UK English. The calculations, the wording shown in the tool, the printed report and the exports are unchanged. The 2,553-bracket enumeration and the 27 random brackets were re-run on 2.7.6 with no difference; the served files matched the release and the page was read. 15/09/2026 (2.7.5): the emergency lighting lines were read back against BS 5266-1:2025, which replaced the 2016 edition. Its clause 8.2 applies to emergency lighting fed from a central power supply system, so the segregation note and the fire-resistant cable line now say so, the cable line cites 8.2.2, and supply cables to self-contained luminaires are named as needing no fire protection (8.1). The wording in the tool and the notes written inside the program code were revised in plain UK English. A new automated check reads every BS 5266-1 citation and the wording of every program file, in the tool, the printed report and the report data, and fails on the 2.7.4 build; the 2,553-bracket enumeration, the 27 random brackets, the 56 hand-calculated checks and the audit checks were re-run on the final build with no difference; no width, load, reaction or rod value changed; the served files matched the release and the page was read. 15/09/2026 (2.7.4): the wording of one line was revised. On a BS 8519 fire route the fire alarm and emergency lighting cable lines now state that the category applies to the supports only, with the drop rods and the containment load checked for the fire survival time; the previous sentence did not say what was checked. The automated check reads the sentence in the tool, the printed report and the report data and fails on the 2.7.3 build; the 2,553-bracket enumeration and the audit checks were re-run on the final build with no difference; no width, load, reaction or rod value changed; the served files matched the release and the page was read. 15/09/2026 (2.7.3): changes from the owner's review of a printed 2.7.2 report. On a BS 8519 fire route the fire-resistant cables on each run are now checked in the tool, in the printed report and in the exports alike; before, the only note sat in the design notes shown in the tool. The check was corrected to the standards at the same time: BS 8519:2020 clause 1 excludes the installations covered by BS 5839-1 and BS 5266-1, so fire alarm cables are referred to BS 5839-1:2025 clause 25 and emergency lighting cables to BS 5266-1, and FP200 Gold is treated as the Category 1 control cable its datasheet declares. The segregation reference now cites BS 5839-1:2025 35.5 (26.2 was the 2017 numbering). BS 8519 is switched on from the Standards applied strip, the tier spacing is asked only on a bracket with more than one tier, and the report headline is coloured by the worst verdict. A new automated check reads the fire cable lines in the tool, the printed report and the exports against the scope of the standard and fails on the 2.7.2 build; the 2,553-bracket enumeration, the 27 random brackets and the audit checks were re-run on the final build with no difference; no width, load, reaction or rod value changed; the served files matched the release and the page was read. 10/09/2026 (2.7.2): the tier spacing, the BS 8519 fire route and the cable category, read only by a fire-rated or multi-tier bracket, moved into a route options section on the add-a-run panel, closed until opened, so the common run needs only its cables, spare and support spacing. Three wording defects found by the owner on the live tool the same evening are corrected: the over-table bracket advice offered a third rod, which a two-rod trapeze cannot take, and now reads reduce the bracket spacing or split the route; the worst rod tile read over table and now names the rod exceeded; and the indicative load check offered a heavier duty to a heavy-duty tray and a shorter span where no tabulated span was rated for the load, and now names only a remedy that passes on the benchmark rows, or says that none does. An automated check tests all four against the benchmark rows and the live page and fails on the 2.7.1 build; the 2,553-bracket enumeration, the 27 random brackets and the audit checks were re-run on the final build with no difference; no width, load, reaction or rod value changed; the served files matched the release and the page was read. 04/09/2026: a full enumeration drove 2,553 brackets through the live engine, every containment type with single-core, multicore and mixed cable sets in flat and trefoil formation, spaced and touching, with and without spare, at two spans and on unrated and fire-rated routes of every category, plus bunched data runs at four depths, trunking by reference at fifteen sizes, three-run brackets across tier layouts and over-width splits. Every width, load, bracket reaction, rod size and tier count matched a separate calculation of the same method from the same data tables. 04/09/2026 (2.7.1): every numeric input was checked for the figure a reader could enter in its place. The custom cable diameter is now defined as the overall diameter over the sheath, not the conductor size; the weight as kilograms per kilometre, with a figure that reads like kilograms per metre flagged in the tool; the support spacing in metres, not the cleat spacing, limited to 12 m and flagged above 6 m; the tier spacing as the clear distance between tray surfaces that Tables 4C4 and 4C5 Note 3 tabulate at 300 mm. No width, load, factor or rod value changed: the 27 random brackets and the audit checks were re-run and all passed, and the script on the live site was confirmed identical to the tested build. 03/09/2026 (2.7.0): a check across every PD tool that every printed value is reached through the input the standard derives it from. The grouping factor was found to count every tier on the bracket as a tray of grouped circuits, including data and AV tiers; it now counts only the tiers with loaded circuits and says which, and asks the vertical spacing between tiers that Tables 4C4 and 4C5 Note 3 assume. The loading verdict now names the duty chosen and is an indicative check against the manufacturer's declared SWL, which can be entered. Single-core cables over 40 mm diameter, which Table D1 does not cover, take the tested cleat centres of the basis product or ask for the manufacturer's figure. A perforated or unperforated tray is now a choice, unperforated reading Reference Method C (Table 4A2). Blank spare, blank custom diameter and blank weight ask for the value. The 56 offline checks and the 27 random brackets were re-run and all passed; after upload, the page was read. 02/09/2026 (2.6.1): the revised wording was checked in the tool against the house style, using the multi-service bracket preset; no size, load or factor changed. Claims audit 14/07/2026: every cited clause was checked against the standard itself (BS 7671:2018+A4:2026 Tables 4A2, 4C1, 4C4, 4C5; OSG Appendix D Table D1; BS 8519:2020 Annex I and Table E.2; BS EN 61439-1 Table 7; BS EN 61537; BS 5839-1:2017 26.2, now BS 5839-1:2025 35.5; BS 5266-1:2025 8.2.6; BEAMA guide); one grouping factor was corrected to the standard as a result. The 56 hand-calculated checks are re-run offline before every release, and the 03/07/2026 audit figures were reproduced on the live v2 engine on 13/07/2026. Randomised cross-check 15/07/2026: 27 random brackets, including a 12-run, 4-tier case, exactly matched a separate calculation of the same method from the same data tables. Grouping Cg reproduces the Trimble ProDesign worked example. Cable data audit 11/08/2026: all 23 BS 5467 SWA rows were checked row by row against the Eland Cables dimensions tables (Issue 04.0913), and the 3-core 25 mm² was cross-checked against the Doncaster and Cleveland datasheets. Three figures were corrected: the 5-core 10 mm² diameter, 22.09 to 22.9 mm, and the 5-core 70 and 95 mm² rows, which had no published source and now follow the Cleveland Cable BS 5467 datasheet, the only one of the five checked that publishes 5-core above 50 mm². The offline checks were re-run on 12/08/2026 after the interface update and all passed.