Engineering Tools
Conduit Fill Calculator
Calculate conduit fill percentage per NEC Article 358 / IEC 61386 standards. Select conduit type and size, add cables, and verify compliance before installation.
Step 1 -- Select Conduit
Internal Diameter
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Internal Area
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Max Fill Area
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Applicable Standard
NEC Table 4
Step 2 -- Add Cables
Area = π × (OD/2)² will be calculated automatically
NEC Fill Rules Reference
| Conductors | Max Fill | NEC Ref. |
|---|---|---|
| 1 conductor | 53% | Table 1, Ch. 9 |
| 2 conductors | 31% | Table 1, Ch. 9 |
| 3+ conductors | 40% | Table 1, Ch. 9 |
| IEC / Custom | 40% | IEC 61386 |
Fill Result
No conduit selected
Fill Ratio
40%
Limit
Conduit Area
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Cable Area
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Remaining Area
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Total Conductors
0
Cables in Conduit
No cables added yet.
Select a cable type and click "Add Cable to Conduit".
| # | Cable / Type | Qty | Unit Area (in²) | Total Area (in²) | Fill % | |
|---|---|---|---|---|---|---|
| Total | -- | -- | -- | |||
Engineering Recommendations
Add cables to receive compliance recommendations and conduit sizing guidance.
Conduit Size Comparison
Fill percentage for current cable set across all trade sizes (same conduit type).
| Trade Size | Int. Area (in²) | Fill % | Max Allowed | Status |
|---|
Disclaimer: This calculator is provided as an engineering reference tool based on NEC Chapter 9 Table 1 and IEC 61386 guidelines. Results are for estimation purposes only. Always verify calculations against the applicable local electrical code, consult a licensed electrical engineer, and follow all authority having jurisdiction (AHJ) requirements. Wire/cable dimensions sourced from NEC Table 5 (THHN/THWN) and manufacturer datasheets. Jinda Cable assumes no liability for installation decisions made based on this tool.