Conduit Fill Calculator
See if these conductors still fit the pipe, and what trade size is next.
Which fill limit applies
Common planning limits used here:
1 conductor: 53%
2 conductors: 31%
3 or more conductors: 40%
Nipples and some local rules differ. This page does not approve a pull. Confirm conductor OD, internal area, and exceptions in the current code and manufacturer data.
How to check a pipe
- Pick the conduit type and trade size in inches.
- Add each AWG, insulation, and count. Include the ground if it is in the pipe.
- Read fill percent, the limit, remaining room, and the next trade size if it is over.
Example: 3×12 AWG THHN plus one 12 AWG ground in 1/2 in EMT
Four 12 AWG THHN planning areas in 1/2 in EMT.
That is under the 40% planning limit for 3 or more conductors.
Example labels: Fill percent about 17–18%. Limit 40%. Vs limit: Fits. Next conduit up: none required by this fill check.
Related tools
Guides for this tool
Conduit fill FAQ
Do I count the equipment-grounding conductor?
Yes, if it is in the pipe. Add it as its own row.
Is 40% always the rule?
No. This page uses the common 53/31/40 planning limits. Nipples and some installations differ.
Does a Fit result mean I can pull it?
No. It is a planning fill check, not a pull approval or a jamming calculation.
Is this free?
Yes. Conduit fill stays free without an account.