Conduit Fill Calculator

How many wires fit in this conduit?

EMT trade size
THHN wire size
wires

Your conduit fill is

10% full

Limit for 4 wires is 40% (Chapter 9 Table 1). EMT with THHN only. Planning figure only. Confirm against the electrical code your area has adopted and have a licensed electrician check the work.

3/4 in EMT4 × #12 THHNFill: 10%Limit: 40%Within the fill limit
Wire area total0.053 sq in
Conduit area0.533 sq in
Max at 40%16 wires
Smallest EMT that passes1/2 in

Check THHN wires in EMT against the percentage limits in the electrical code Chapter 9.

How it works

Adds the Table 5 area of every wire, divides by the Table 4 inside area of the conduit, and compares to the Table 1 limit: 53% for one wire, 31% for two, 40% for three or more.

Before you order

  • Count every conductor, including neutrals and grounds, because they all take up room.
  • Pulling is easier well under the limit, especially on runs with several bends.
  • Bundling many current-carrying wires can reduce their ampacity even when the fill passes.

Common questions

Why are 4 and 3 AWG missing?

We only list wire sizes where we could confirm the published area, so those two and any conduit over 1-1/2 in are left out for now.

Can I use this for PVC?

Not as written. PVC has a smaller inside area than EMT of the same trade size, so use the PVC column in Table 4.