314.16(A): Metal Box Fill

Maximum number of conductors permitted in various sizes of standard metal boxes.

Source: NEC 2020

The Math Shortcut

Use the Box Fill Calculator

Box Size (in)	Min. Volume (in³)	14 AWG	12 AWG	10 AWG
4 x 1-1/4 Round	12.5	6	5	5
4 x 1-1/2 Round	15.5	7	6	6
4 x 2-1/8 Round	21.5	10	9	8
4 x 1-1/4 Square	18.0	9	8	7
4 x 1-1/2 Square	21.0	10	9	8
4 x 2-1/8 Square	30.3	15	13	12

Related NEC Tables

Table 314.16(B): Volume Allowances

Professional Usage

This data is provided for informational purposes only. Always verify with the latest edition of the National Electrical Code (NFPA 70) and consult with a licensed electrical professional or AHJ (Authority Having Jurisdiction) before performing any electrical work.

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