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# Conduit fill calculator

Add cables to a conduit, see the fill percent against the limit, and get the smallest conduit that fits with room to spare.

NEC mode reads the Chapter 9 Table 4 EMT series with the Table 1 limits: 53 % for one conductor, 31 % for two, 40 % for three or more, earth wires counted. The 600 mm nipple exception (60 %) is not modelled. IEC mode applies the 40 % conduit convention over the nominal IEC sizes with indicative medium-duty internal diameters; real internal bores vary by maker, so treat the IEC result as indicative too, and trunking as a different animal. Fill is not ampacity: nine current-carrying conductors can pass fill and still need a 70 % ampacity adjustment that forces bigger cables which then do not fit. The indicative preset diameters are not for ordering.
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