What it calculates
Estimate conductor fill area and fill percentage.
Conduit Fill Planning Calculator
Estimate conduit fill percentage from conduit inside area, conductor area and conductor count.
Planning and estimating aid only. Verify project requirements, manufacturer instructions, adopted codes, permits, and field conditions before performing regulated work.
Electrical planning
How to Use This Calculator
Use the field units shown below, then compare your result with the worked example. This model assumes all conductors have the same area.
How the calculation works
Total conductor area = area per conductor × conductor count. Fill percentage = total conductor area ÷ conduit inside area × 100.
What the result means
Compare the result with the allowable fill for the exact raceway and conductor combination.
Compare occupied area with the entered conduit area
Three identical conductors at 0.05 square inches each occupy 0.15 square inches. Dividing by an entered conduit area of 0.5 square inches gives 0.30, or 30% fill.
Contractor tip: This model assumes all conductors have the same area. For mixed sizes, add their individual occupied areas separately and compare against the applicable permitted fill for that exact installation.
Verify the final quantity
Use actual insulated conductor cross-sectional areas and the internal area for the exact raceway. Nominal trade size is not the internal area, and this tool does not determine an allowed fill percentage.
Good practice: Compare the calculated quantity with plans, specifications, product packaging and current field conditions before purchasing material.