VOLTAGEDROPCALCULATOR
Raceway Planning Tool

Conduit FillCalculator

Estimate raceway fill for common THHN/THWN-2 conductor groupings before you finalize conduit size and layout.

Estimate conduit fill for common THHN/THWN-2 conductor groupings using standard single-conductor areas and the familiar NEC Chapter 9 fill limits: 53% for one conductor, 31% for two, and 40% for three or more. Verify compact-stranded cable dimensions, cable assemblies, nipples, and any manufacturer-specific data before issuing final drawings or installing material.

Conduit Inputs

common THHN/THWN-2 conductors in a selected raceway

Phase / hot conductors

Identical insulated conductors in the same raceway

Neutral conductors

Identical insulated conductors in the same raceway

Equipment grounding conductors

Identical insulated conductors in the same raceway

Fill Summary

Area-based raceway check

Selected raceway exceeds fill limits

EMT 1" is at 123.2% of the allowable fill area for 5 conductors.

Total conductor area
0.426 in²
Allowable fill area
0.346 in²
Fill rule used
40.0%
Recommended trade size
1-1/4"

Conductor breakdown

Phase / hot conductors
3 × 3 AWG at 0.0973 in² each
0.292 in²
Neutral conductors
1 × 3 AWG at 0.0973 in² each
0.097 in²
Equipment grounding conductors
1 × 8 AWG at 0.0366 in² each
0.037 in²

Raceway sizes

1/2"
Allowable area 0.122 in²
350.2%
Over
3/4"
Allowable area 0.213 in²
199.7%
Over
1"
Allowable area 0.346 in²
123.2%
Over
1-1/4"
Allowable area 0.598 in²
71.2%
Pass
1-1/2"
Allowable area 0.814 in²
52.3%
Pass
2"
Allowable area 1.342 in²
31.7%
Pass
2-1/2"
Allowable area 2.343 in²
18.2%
Pass
3"
Allowable area 3.538 in²
12.0%
Pass
3-1/2"
Allowable area 4.863 in²
8.8%
Pass
4"
Allowable area 7.356 in²
5.8%
Pass
Field Notes
  • This tool assumes individual THHN/THWN-2 insulated conductors, not multiconductor cable, MC cable, or manufacturer-specific compact cable dimensions.
  • Raceway fill is only one check. Final design still needs ampacity, temperature correction, bundling, termination, and pulling-tension review.
  • Very short nipples and special conditions can use different NEC rules. Treat this as a planning and coordination tool, not automatic approval.
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