Box Fill

Cubic-inch fill by box volume and conductor count.

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Formula and source

Sum of conductor, device-yoke, clamp, and grounding allowances per NEC 314.16(B), volumes from 314.16(B)(1) keyed to the largest conductor in the box.

NEC 2023 (NFPA 70). Section 314.16.

Audience

This tile is built for electricians and the adjacent professions in the Electrical group. The interactive calculator runs entirely in your browser. No account, no fee, no advertising, no tracking.

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Posture

Rough Logic answers the math question the working professional asks on the job. The site is a calm, fast, ad-free, account-free, ever-free reference. It does not interpret code. It does not replace the licensed professional. It does not store your inputs. The Authority Having Jurisdiction governs all installations and inspections.