Wireman · Conduit fill calculator · 2023 NEC ·
Raceway & boxes
Conduit fill calculator
Add every wire going in the pipe, grounds included. It tells you if they fit and the smallest pipe that works.
How this is calculated
- Conductor areas come from Chapter 9, Table 5. Raceway areas come from Chapter 9, Table 4.
- Allowed fill per Chapter 9, Table 1: 53% for one conductor, 31% for two, 40% for three or more. Nipples 24 in. or shorter may be filled to 60% (Note 4).
- Count equipment grounding and bonding conductors (Note 3). Bare conductors use Table 8 areas, which aren't included yet.
- More than three current-carrying conductors in one raceway means derating. The wire size calculator handles that.