Ft / In · Box FillConcrete · Lumber · DrywallPaint · Stairs · Framing
01Box
Table 314.16(A)
Nonmetallic and sectional boxes must be durably marked with their volume — enter that marked value as a custom volume. Plaster-ring or extension volumes marked in in³ may be added to it.
02Circuit conductors
314.16(B)(1)
Quick add cable
18 AWG
1.50 in³ ea
16 AWG
1.75 in³ ea
14 AWG
2.00 in³ ea
12 AWG
2.25 in³ ea
10 AWG
2.50 in³ ea
8 AWG
3.00 in³ ea
6 AWG
5.00 in³ ea
4 AWG
5.00 in³ ea
3 AWG
5.00 in³ ea
2 AWG
5.00 in³ ea
1 AWG
8.00 in³ ea
1/0 AWG
8.00 in³ ea
2/0 AWG
8.00 in³ ea
3/0 AWG
8.00 in³ ea
4/0 AWG
8.00 in³ ea
Count each insulated conductor that enters and is spliced or terminated in the box, and each conductor passing through unbroken (count it twice if looped with at least 12 in. of free conductor). Don't count pigtails that never leave the box, or equipment grounding conductors — those go in section 05.
03Clamps & support fittings
314.16(B)(2)–(3)
Each allowance is based on the largest conductor in the box. Connectors that clamp the cable outside the box (locknut-style NM connectors) don't count.
04Devices (yokes / straps)
314.16(B)(4)
No devices yet. Each receptacle, switch, or dimmer on its own yoke counts as two conductor allowances.
05Equipment grounding conductors
314.16(B)(5)
EGCs entering box
1 allowance for up to 4, then ¼ each
Planning estimates only. Confirm coverage rates on product labels, check local building code and the NEC edition adopted in your jurisdiction, and order a little extra when cutting waste or site conditions are uncertain.