NEC 314.16(B) volume allowances — conductors, devices, clamps, and grounds — checked against the standard box volumes in Table 314.16(A). The way the exam asks it. Free, no signup.
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Volume allowances per NEC Table 314.16(B); box volumes per Table 314.16(A). Counting rules (314.16(B)): each conductor entering and terminating or passing through = 1 allowance at its own size; all internal cable clamps together = 1; each support fitting (stud/hickey) = 1; each device yoke/strap = 2; all equipment grounding conductors together = 1 (a second isolated-ground set = 1 more). Non-conductor items use the largest conductor in the box. Conductors originating and ending inside the box (pigtails) are not counted; a conductor looped without a splice and at least twice the free-conductor length counts as 2. This tool assumes one conductor size — for mixed sizes, sum each size separately.
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