Conduit Fill Calculator

A conduit fill calculator that follows NEC Chapter 9, applying the Table 1 limits of 53 percent for one conductor, 31 percent for two and 40 percent for three or more to the Table 4 conduit areas. Pick the conduit type, the trade size and a THHN or THWN-2 conductor size, and it either checks a pull you have already planned or tells you how many conductors of that size fit. The conductor areas come from the Table 5 THHN/THWN-2 column, so another insulation has a different area, and a mix of sizes has to be added up by hand. Verify the result against the code edition your jurisdiction has adopted, because the local inspector's reading governs the job.