Junction Box Fill Calculator
Quickly calculate the minimum volume required for electrical device and outlet boxes according to National Electrical Code (NEC) Section 314.16.
Box Contents Input
1. Circuit Conductors (Hot / Neutral Wires)
2. Equipment Grounding Wires
3. Devices (Switches / Outlets)
Enter the count of device yokes connected to each wire size:
4. Fitting Allowances
Required Box Volume
Minimum Volume Required
0.00 in³
NEC Section 314.16 code-compliant capacity
Detailed Calculation Breakdown:
Compatible Standard Box Sizes:
3 x 2 x 2 Device Box
3 x 2 x 2 in
4 x 2-1/8 x 1-7/8 Handy Box
4 x 2-1/8 x 1-7/8 in
3 x 2 x 2-1/4 Device Box
3 x 2 x 2-1/4 in
4 x 1-1/4 Round/Octagonal
4 x 1-1/4 in
3 x 2 x 2-1/2 Device Box
3 x 2 x 2-1/2 in
4 x 2-1/8 x 2-1/8 Handy Box
4 x 2-1/8 x 2-1/8 in
3 x 2 x 2-3/4 Device Box
3 x 2 x 2-3/4 in
4 x 1-1/2 Round/Octagonal
4 x 1-1/2 in
4 x 1-1/4 Square
4 x 1-1/4 in
3 x 2 x 3-1/2 Device Box
3 x 2 x 3-1/2 in
4 x 1-1/2 Square
4 x 1-1/2 in
4 x 2-1/8 Round/Octagonal
4 x 2-1/8 in
4-11/16 x 1-1/2 Square
4-11/16 x 1-1/2 in
4 x 2-1/8 Square
4 x 2-1/8 in
4-11/16 x 2-1/8 Square
4-11/16 x 2-1/8 in
Frequently Asked Questions
Built for electrical professionals by SpliceJobs
Disclaimer: This tool provides calculations based on standard National Electrical Code (NEC) values. Always verify box volumes and conduit entries with your local authority having jurisdiction.