Electrical Boxes

Electrical boxes sized by volume math instead of guesswork, with metal and PVC options in stock and ready to ship with free shipping on every order and no minimums. The NEC 314.16 fill table below the products puts cubic inch capacities and conductor counts in one place.

Products List

Sort By:

Display Type:
Filters
  • Product
  • Qty in Cart
  • Quantity
  • Price
  • Subtotal
  • Total: items /

Adding your products to cart

View Cart Continue Shopping

Electrical Box Selection Guide

Junction Boxes, Outlet Boxes, and J Boxes

The terminology sorts by what happens inside. A junction box (the j box on a jobsite) closes over spliced conductors with a blank cover, an outlet box carries a receptacle, switch, or fixture on a mounting yoke, and ceiling-rated octagon boxes support lightweight fixtures directly. The same 4 inch square box often plays all three roles depending on the cover installed, which is why square boxes with mud rings dominate commercial rough-in. Anything living outdoors or in a washdown area needs a listed weatherproof enclosure with the right cover; those are separated into Weatherproof Boxes, including in-use covers for receptacles in wet locations.

Boxes Are the Cheap Part; Stocking Out Is Not

An electrician who runs out of boxes mid-rough-in loses the day, which is a bad trade for parts that cost a few dollars each. There are no order minimums here, shipping is free on every order, and stock status shows live on each product page, so ordering electrical boxes for the whole floor plus spares is painless. The rest of the rough-in lives one category over: Conduit Fittings for connectors and couplings, Ground Clamps for bonding, Wire and Cable for what runs into the box, and Wire Connectors for what happens inside it. Questions on a fill calculation or an oddball configuration? Call a specialist at 855-775-4533.

Electrical Boxes Sized by the NEC 314.16 Fill Table

The fastest way to pick an electrical box is volume math, not guesswork. NEC 314.16 assigns each conductor a volume allowance, 2.0 cubic inches for 14 AWG and 2.25 for 12 AWG, and the box must have enough cubic inches to cover everything landing in it. Big-box category grids make you dig for cubic-inch ratings one product at a time; this table puts the standard sizes and their raw conductor capacities in one place.

BoxVolume (cu in)Max 14 AWG ConductorsMax 12 AWG Conductors
Metal device box, 3 x 2 x 2-1/2 in12.565
4 in octagon box, 1-1/2 in deep15.576
Single-gang nonmetallic nail-on (typical)18.098
4 in square box, 1-1/2 in deep21.0109
4 in square box, 2-1/8 in deep30.31513
4-11/16 in square box, 2-1/8 in deep42.02118

Those counts are raw conductor allowances; the full 314.16 calculation subtracts more. A device on a yoke counts as two allowances of the largest conductor connected to it, all internal cable clamps together count as one, and equipment grounding conductors take at least one full allowance, with the exact grounding count depending on the NEC edition adopted in your jurisdiction. When the math lands close to the limit, step up to the deeper box or add an extension ring; nobody has ever regretted the extra cubic inches at trim-out.

Metal or PVC

Metal electrical boxes are the commercial default wherever conduit systems run, because the raceway typically serves as the grounding path and must bond through the enclosure. Nonmetallic boxes rule wood-frame construction with NM cable: cheaper, faster, and no bonding screw to forget. The rough split holds across most jobs, with metal for EMT and rigid conduit work, and PVC or fiberglass where cable arrives without a raceway.

Frequently Asked Questions About Electrical Boxes

Total the NEC 314.16 volume allowances for everything in the box: 2.0 cubic inches per 14 AWG conductor, 2.25 per 12 AWG, two allowances for each device yoke, one for all internal clamps combined, and at least one for the grounding conductors. Then choose a box whose cubic-inch rating meets or exceeds the total. When in doubt, size up.

Use metal wherever a metallic conduit system (EMT, rigid, flexible metal conduit) enters the box, because the raceway usually serves as the equipment grounding path and must bond through the enclosure. Metal is also standard in commercial construction generally. Nonmetallic boxes suit wood-frame work with NM cable, where they install faster and cost less.

Box fill is the NEC 314.16 calculation that limits how many conductors, devices, and clamps can occupy a box of a given volume. Overfilled boxes cramp conductors, damage insulation, trap heat, and fail inspection. Every box in this category lists its cubic-inch rating, so you can run the math before ordering rather than discovering a violation at rough-in inspection.

Yes. The distinction is use, not construction: cover a standard box with a blank plate over spliced conductors and it functions as a junction box, provided fill limits are respected and the cover remains accessible. The reverse also holds, since a 4 inch square junction box takes a mud ring to mount a device. Buried or concealed splices are never permitted.

A weatherproof-rated enclosure matched to the location: damp-rated for protected areas like covered porches, wet-rated for anything exposed to rain or washdown. Receptacles in wet locations also need an in-use (bubble) cover that maintains the rating with a cord plugged in. Standard interior boxes, metal or plastic, are not listed for either condition.

A 1-1/2 inch deep 4 inch square box provides 21 cubic inches, which works out to ten 14 AWG or nine 12 AWG conductor allowances before deductions for devices, clamps, and grounds. The 2-1/8 inch deep version raises that to 30.3 cubic inches, or fifteen and thirteen respectively. Extension rings add volume when a run grows beyond the original calculation.

Yes. Equipment grounding conductors take at least one full volume allowance based on the largest grounding conductor in the box, and recent NEC editions add a further quarter allowance per additional ground beyond four. Since adopted editions vary by state, check the code year your jurisdiction enforces; the safe move is simply choosing a box with comfortable margin.