Conduit Fill Calculator
Estimate how full a conduit may be based on conduit type, conduit size, wire size, and conductor count.
Conduit fill is a quick way to see how much space the wires may take up inside the raceway. Higher fill can mean a tougher pull and less room to work.
This estimator gives a quick sense of how crowded the conduit may be. Different conduit types can have different internal space even when the trade size sounds the same.
Choose the conduit and wire details to estimate the fill level.
Estimated result
Estimated fill percentage
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Status
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Conduit selected
EMT 3/4"
Wire and conductor summary
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Minimum workable conduit size
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Roomier option
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Plain-English note
Run the estimator to see whether the selected conduit looks roomy, tight, or likely overfilled.
Recommendation
Run the estimator to see whether the selected conduit size is comfortable or whether moving up a size would help.
How to read conduit fill
Conduit fill is about how much space the wires take up inside the raceway
The same trade size can have different usable space depending on the conduit type
Ground wires still count for physical fill, even if their sizing can differ from the phase conductors
Tighter fill can make pulling conductors harder even before you hit a formal limit
Reference approach used
Common wire sizes
The estimator uses simplified area values for common building wire sizes from 14 AWG through 2 AWG.
Conduit families
EMT, PVC Schedule 40, PVC Schedule 80, RMC, IMC, FMC, LFMC, and ENT use different simplified usable fill values so the estimator reflects their different internal dimensions.
This calculator is a simplified planning estimator only. Actual conduit fill depends on conductor insulation, wire type, raceway type, code rules, grounding requirements, and installation details. For more precise conduit fill calculations, refer to NEC Chapter 9 tables or applicable local codes. This tool is intended as a practical planning reference. When in doubt, check the applicable code tables or ask a licensed electrician.
Related problems and reference
Planning and safety note
This content is for general learning and planning. Always verify work against current NEC requirements, manufacturer instructions, and local code rules. If you are unsure or see heat, sparks, burning smell, repeated trips, or damaged wiring, contact a licensed electrician.