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Do you need to calculate a box size given the wires that are going into the box? Construction Monkey has the perfect calculator for you. Just answer the questions below and we will do the box fill calculations for you based on Article 314.16 of the National Electrical Code.

Data Results
Number of Wires Terminating in the Box
Per NEC 314.16(B)(1) Enter each conductor that originates outside the box and terminates in the box.
#14 #12 #10 #8 #6
Number of Wires Spliced in the Box
Per NEC 314.16(B)(1) Enter each conductor that originates outside the box and is spliced in the box.
#14 #12 #10 #8 #6
Number of Wires that Pass Thru Box
Per NEC 314.16(B)(1) Enter each conductor that pass through the box without splice or termination.
#14 #12 #10 #8 #6
Number of Wire Loops Greater than 12"
Per NEC 314.16(B)(1) Enter each loop or coil of unbroken conductor that is at least 12" in length.
#14 #12 #10 #8 #6
Additional Information
Are there any internal wire clamps to the box?
Number of Luminaire Studs or Hickeys that mount to the box or cover:
Number (Gang) of Devices to be mounted to the box:
Largest Wire Size Connecting to Devices:
Size of Equipment Grounding Conductor that enters the box:
Allowances for #14 Wires N/A
Allowances for #12 Wires N/A
Allowances for #10 Wires N/A
Allowances for #8 Wires N/A
Allowances for #6 Wires N/A
Total Wire Allowances N/A
Additional Allowance for Wire Clamps N/A
Additional Allowance for Luminaire Studs N/A
Additional Allowance for Devices N/A
Additional Allowance for Equip. Grounding Cond. N/A
Minimum Allowable Box Size N/A
No guarantees are made as to the accuracy of the calculation or compliance with local codes.  Verify all calculations with a professional engineer. If you find an error, or have a suggestion, please send us an email.