Conduit Fill Calculator
Check whether your conductor combination fits within NEC raceway fill limits per Chapter 9, Table 1: one conductor up to 53%, two conductors up to 31%, three or more up to 40%. Pick the raceway type and trade size, then add conductors. The calculator sums conductor areas from Chapter 9 Table 5 and compares against the raceway internal area from Table 4.
Conductor area
0.0399 sq in
3 conductors
Allowed at 40%
0.3456 sq in
Raceway internal: 0.8640 sq in
Fill: 4.62% of internal area
✓ PASS — within NEC fill limitsNEC fill limits (Chapter 9, Table 1)
- • 1 conductor: 53% maximum fill
- • 2 conductors: 31% maximum fill
- • 3 or more conductors: 40% maximum fill
For lead-sheathed cables and certain other special conditions, different fill limits apply — see Chapter 9 Notes.
Test your knowledge
Practice raceway and conductor problems with these tests:
Educational tool only. Verify against the current NEC.