Real conduit installations often contain conductors of different wire sizes — for example, a conduit might carry 4 AWG circuit conductors, 12 AWG control wiring, and a 6 AWG equipment grounding conductor. When different sizes are mixed in a single conduit, you cannot use NEC Annex C (which provides maximum conductor counts for uniform sizes). Instead, you must use the cross-sectional area method from NEC Chapter 9: sum the actual cross-sectional area of every conductor from Table 5, then check that the total does not exceed 40% of the conduit's internal area. This calculator performs the cross-sectional area sum for any combination of conductor sizes and types.
1-1/4" EMT (1.496 sq in, 40% = 0.598 sq in). Conductors: 3 × 4 AWG THHN (0.0824) = 0.247; 2 × 12 AWG THHN (0.0133) = 0.027; 1 × 10 AWG THHN (0.0211) = 0.021. Total = 0.295 sq in (19.7%). Within 40% limit.
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.
Try all options in the full Conduit Fill Calculator →