Observed arrival · 2026-10-14
Conduitwise’s NEC conduit-fill calculator
A free calculator estimates conduit fill from wire type, gauge, count, and conduit choice, then identifies the smallest size that fits.
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- Electricians and DIYers sizing conductors in conduit
- Worth noticing
- The site reports checking 300 random wire mixes across EMT, PVC Schedule 40, and rigid metal conduit with zero differences.
Field notes
Users choose conduit type and trade size, then add THHN/THWN/THWN-2 conductors by gauge and count; the page returns total area, applicable fill limit, fill percentage, and smallest fitting size. It lays out the Table 1 percentages and Table 4/5 values alongside worked examples. The site says it re-entered the tables and checked 300 random combinations across EMT, PVC Schedule 40, and rigid metal conduit; its stated source cross-check is the 2017 NEC edition.
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