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Conduit Fill Calculator

Check conduit fill (40% rule) for THHN/THWN-2 conductors in EMT and PVC Schedule 40 conduit from 1/2" to 2", and see how many wires fit.

Conduit

Wire (THHN/THWN-2)

Number of wires

How to use it

Pick the conduit trade size and type.
Pick the wire size (THHN/THWN-2) and how many conductors, including grounds.
Fill must stay at or under 40% for 3 or more wires (31% for two, 53% for one).

How it works

Fill % = (number × wire area) ÷ conduit internal area. Areas from NEC Chapter 9 Tables 4 and 5. For mixed sizes, add the areas of each wire.

FAQ

How many 12 gauge wires fit in 3/4 EMT?

16 THHN 12 AWG conductors fit in 3/4" EMT at 40% fill.

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