Electrical metallic tubing (EMT) is the most common raceway type in commercial and light industrial construction. NEC Chapter 9, Table 1 limits EMT fill to 40% of the internal cross-sectional area when three or more conductors are installed (53% for two conductors, 31% for one conductor). EMT internal diameters are standardized by trade size: 1/2" EMT has 0.304 sq in usable area, 3/4" has 0.533 sq in, 1" has 0.864 sq in, and 1-1/4" has 1.496 sq in. This calculator uses NEC Annex C Table C1 for EMT and accounts for each conductor's cross-sectional area based on wire type and AWG size.
3/4" EMT (0.533 sq in at 40%): allowable fill = 0.213 sq in. Four 12 AWG THHN conductors: 4 × 0.0133 sq in = 0.0532 sq in. Fill = 0.0532 / 0.533 = 9.98%. Well within 40% limit. Could fit up to 16 conductors of 12 AWG THHN.
This is a variant of the full Conduit Fill Calculator — which supports EMT, PVC, RMC, IMC, and flexible conduit with any conductor type and size.
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