California State License No. 989035Residential & Commercial Electrical Contractor

HAIK ELECTRIC · ELECTRICAL CHARTS & REFERENCES

Conduit Fill Chart & Calculator

Compare EMT, IMC, and RMC. Check mixed conductor sizes, find a minimum trade size, and print your reference chart.

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Conductors & cables

Include insulated or bare grounding conductors in the occupied area. For other insulation types or cables, select Custom and enter the complete outside diameter. A multiconductor cable counts as one cable; use its overall diameter, or its major diameter if oval.

Conduit fill chart

Counts are conservative calculated capacities for identical THHN/THWN-2 conductors. The calculator uses occupied area without the optional same-size rounding allowance. A dash means no conductor of that size fits. Mixed sizes require the calculator above.

Allowable fill

1 conductor / cable

53% of internal area

2 conductors / cables

31% of internal area

3 or more

40% of internal area

Eligible short nipple

60% of internal area

Method & reference sources

Fill = total conductor/cable area ÷ conduit internal area × 100. Custom circular area = π × outside diameter² ÷ 4. Standard conduit areas and THHN/THWN-2 conductor areas follow NEC Chapter 9, Tables 4 and 5; fill rules follow Table 1. Supported trade sizes: ½–4 inches. Minimum size means minimum within this supported range.

Fill check only. Ampacity adjustments, pulling difficulty, jam risk, bending limits, and local amendments require separate review. Verify the locally adopted NEC edition and actual cable construction before installation. A fill result does not determine ampacity.

Reference reviewed October 2026. Manufacturer nominal dimensions may differ slightly from rounded code-table areas.