Cable to Conduit Size Calculator – Free Electrical Tool

Electrical Engineering Tool

⚡ Cable-to-Conduit Size Calculator

Calculate the required conduit area and select the smallest standard conduit for multiple cable sizes and quantities installed in the same conduit.

Cable Schedule in This Conduit

Cable	Type	Size	Qty	OD	Area × Qty

Calculation Results

Total Area of All Cables –

Minimum Spare Space –

Required Conduit Area –

✅ Recommended Standard Conduit –

Next Larger Standard Size –

Recommended Conduit Internal Area –

Calculated Utilization –

Maximum Cable Fill –

Cable Outside Diameter –

How is the conduit size calculated?

1. Cable area: each cable type uses its selected outside diameter (OD) to calculate the cross-sectional area of one cable.

A = π × (OD / 2)²

2. Total cable area: each cable group area is multiplied by its quantity, then all cable groups are added together.

A(total) = Σ [ A(cable type) × Quantity ]

3. Required conduit area: total cable area is divided by the the maximum allowable cable fill (100% minus the selected spare-space percentage).

Maximum Fill = 100% − Spare Space%\nA(required) = A(total) ÷ (Maximum Fill / 100)

4. Recommendation: the smallest listed standard conduit whose internal circular area is equal to or greater than the required area is selected.

ℹ Mixed Cable Sizes Multiple cable sizes and quantities can be entered in the same conduit. The calculator adds the area of every cable group before applying the selected spare-space requirement.

⚠ Important Safety & Accuracy Disclaimer This tool provides estimates only using the cable outside-diameter data and standard conduit IDs contained in this calculator. The minimum spare-space percentage is user-defined and is converted to maximum allowable cable fill. Always verify the exact cable OD, conduit internal diameter, installation conditions, applicable electrical code, and project specification before finalizing an installation. Professional engineering judgment is required.