Conduit Fill Calculator
Calculate the maximum number of wires allowed in a conduit based on wire gauge, conduit size, and material. Complies with NEC 2020 fill tables.
Published by:
isCalculator Editorial Team
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How to use this tool?
How to Use the Conduit Fill Calculator
- Select Conduit Type – Choose from PVC Schedule 40, EMT, IMC, or RMC.
- Select Conduit Size – Pick the trade size (e.g., 1/2", 1", 2") from the dropdown.
- Select Wire Gauge – Choose the AWG size (14 to 1 AWG).
- Enter Number of Wires – Input the current number of wires (minimum 1).
- Click "Calculate" – The tool computes the fill percentage and checks compliance with the 40% maximum fill rule.
Output:
- Fill Percentage – Shows the calculated fill as a percentage.
- Compliance Status – "Compliant" (green) if ≤40%, or "Overfilled" (red) if exceeded.
- Explanation – Displays the calculation steps and the maximum additional wires allowed.
Note: All wire areas and conduit areas are in square inches (imperial). The calculator uses standard NEC fill data for common wire gauges and conduit sizes.
Previous Results
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Frequently Asked Questions
Conduit fill is the percentage of cross-sectional area of a conduit occupied by wires. NEC limits it to 40% for more than 2 wires.
Yes, it uses NEC 2020 fill tables for common wire gauges and conduit types.
No, this calculator is based on THHN/THWN copper wire dimensions. For aluminum, use different wire area values.