Which NEC article covers box volumes and box-fill calculations?

• A. Wiring methods and materials.
• B. Box volumes and box-fill calculations.
• C. Grounding and bonding.
• D. Overcurrent protection.

Answer: (B)

Box volumes and box-fill calculations are the part of the NEC that deals with enclosures and how much space inside a box is required for all the conductors and devices it contains. The rule set for this lives in Article 314, which covers Boxes, Conduit Bodies, and Fittings and specifies the minimum internal volume a box must have. The idea behind box-fill is practical: you need enough cubic inches inside the box to physically and safely fit every conductor, grounding conductor, device yoke, and any internal clamp or splice. The calculation works by counting conductors that terminate or are spliced inside the box, counting all equipment grounding conductors as a single total, adding for any internal clamps, and counting the device yokes for switches or receptacles. Add all those up and compare to the box’s actual volume; if the box meets or exceeds the required volume, it’s compliant.

The correct option matches this topic directly. The other options point to different NEC areas—wiring methods and materials, grounding and bonding, or overcurrent protection—which are covered by other articles.