Conduit Fill Chart

Conduit can only be filled to 40% with three or more conductors, to allow heat dissipation and pulling. This chart gives the max number of THHN conductors for common EMT sizes.

EMT conduit 12 AWG THHN 10 AWG THHN
1/2 in 9 5
3/4 in 16 10
1 in 26 16
1-1/4 in 45 28
Watch derating too. When more than three current-carrying conductors share a conduit, their ampacity must be derated. Always follow NEC fill and derating tables for your wire type.

See the Electrical Box Fill Chart and Wire Ampacity Chart.

Related Calculators

Related Guides

Related Guides

Scroll to Top

The calculators and tools on Formula Factory are provided for general guidance and informational purposes only. Results are estimates based on standard formulas and the values you enter — they do not constitute professional engineering, electrical, or architectural advice. Always verify calculations with a qualified professional before making decisions for any safety-critical, code-compliance, or commercial application. Formula Factory makes no representations or warranties as to the accuracy or completeness of any result, and accepts no liability for errors, omissions, or any outcomes arising from reliance on this information.