Conduit Fill & Box Fill Calculator

Reference helper for common field checks. Results are guidance only; verify all work against the applicable code and manufacturer data.

Conduit Fill

Mode

Conduit internal diameter (in)

You can enter ID from a chart. Area is computed automatically.

Allowable fill by conductor count

Conductors

Add each conductor type by outside diameter (in). We sum areas.

Total conductors: 0

Results

Conduit area: 0.0000 in²

Allowable fill area: 0.0000 in² (at 0%)

Sum of conductor areas: 0.0000 in²

Status: Waiting for inputs…

Auto rule picks 53% for one conductor, 31% for two, and 40% for three or more.

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Box Fill

Box internal volume (in³)

Use manufacturer data or measured internal volume.

Largest conductor gauge in box (AWG)

Used for device yokes and equipment grounds equivalences.

Conductor Groups

Each group: gauge and quantity of insulated conductors that originate/terminate or pass through.

Device yokes

Each yoke counts as two conductors of the largest gauge present on that device.

Equipment grounds (total)

All grounds together count as one conductor of the largest gauge present.

Pigtails (do not leave the box)

Pigtails typically do not add to count when spliced only within the box.

Results

Per-conductor volume (by gauge): 2.25 in³

Total conductor equivalents: 0

Required volume: 0.00 in³

Box volume: 0.00 in³

Status: Waiting for inputs…

Per-conductor volumes follow a common reference mapping for typical copper conductors. Verify against current requirements.

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