Conduit Fill Calculator

Inputs

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Use one group for same-size conductors, or add second/third groups for mixed wire sizes.
Conductor insulation type and size. Fill uses the outside area of the insulated conductor, not bare copper area.
Count each conductor occupying conduit area. Mixed sizes should be summed separately; this calculator screens same-size conductors.
Conduit type and trade size. Use the exact internal area for the raceway actually being installed.
Standard raceway fill uses conductor-count limits. Short nipples can use the 60% screen when the code condition applies.

Results

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Conduit fill(F)
22.5%
Pass

3/4 EMT (0.533 in²) passes for 9 conductors.

Also computed

Fill limit40%

three-or-more conductor rule

Max primary-size conductorsPass16conductors

if all conductors are #12 THHN/THWN-2

Conductor area total0.1197in²

Allowable area0.2132in²

Remaining fill area0.0935in²

Method notes 3 notes
  • Groups included: 9 x #12 THHN/THWN-2. Selected conduit internal area: 0.533 in².
  • For mixed conductor sizes, fill is based on the summed insulation area. The maximum primary-size conductor output is a same-size reference only.
  • Conduit fill is not ampacity adjustment, box fill, bend radius, pulling tension or equipment-grounding-conductor sizing. Verify final work against the adopted NEC edition, local amendments and manufacturer dimensions.

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