Box Fill Calculator for Electricians
A free NEC 314.16 box fill calculator that itemizes every conductor, device, clamp, grounding, support-fitting, and terminal-block allowance in the breakdown, so you can calculate box fill and confirm the installation is code-compliant.
Box Fill Calculator
Calculate electrical box fill requirements per NEC 314.16
Box Volume (cu.in.)
18 cu.in.
NEC 314.16(B)(3): one allowance per type of fitting (stud or hickey), not per piece.
Total Fill Required
18.00 cu.in.
Box Capacity
18.00 cu.in.
Remaining Capacity
0.00 cu.in.
Volume Breakdown:
Why Use Our Box Fill Calculator?
A free box fill calculator that shows the full NEC 314.16 volume breakdown component by component, so you can check the result and defend it during layout, inspection, or rework.
How the Box Fill Calculator Works
Three simple steps to calculate electrical box fill per NEC 314.16
Select Box Type
Choose from standard electrical box sizes or enter custom dimensions for your box fill calculation.
Add Components
Enter conductors, devices, clamps, and grounding wires for accurate box fill calculation.
Get Box Fill Results
Instantly see if your electrical box meets NEC 314.16 box fill requirements.
Box Fill Calculator FAQ
Ready to Calculate Box Fill?
Ensure your electrical installations meet NEC 314.16 requirements with our free box fill calculator, including the 2023 terminal-block allowance under 314.16(B)(6).
Start Box Fill Calculator