PVC conduit is widely used in underground, wet, and corrosive environments where EMT's metallic construction would be unsuitable. Schedule 40 PVC has a larger inside diameter than Schedule 80 PVC at the same trade size — which means Schedule 80 allows fewer conductors for a given fill percentage. The fill limits from NEC Chapter 9 Table 1 apply equally to PVC: 40% for three or more conductors. When transitioning from underground PVC to EMT above slab, the fill calculation should be performed for the PVC section (the tighter constraint). This calculator supports both Schedule 40 and Schedule 80 PVC using the correct NEC Annex C tables for each.
1" Schedule 40 PVC (0.864 sq in internal area): 40% fill = 0.346 sq in. Three 6 AWG THHN conductors: 3 × 0.0507 sq in = 0.152 sq in. Fill = 17.6%. 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 →