Laundry Receptacle Box Fill Guide
Use this guide for washer receptacles, 20 amp laundry branch circuits, GFCI devices, feed-through wiring, and tight laundry-room boxes.
Why laundry receptacle boxes get crowded
A laundry receptacle is an outlet that serves laundry equipment such as a washing machine, laundry sink area, or related appliance location. Under NEC 210.11(C)(2) and 210.52(F), dwelling laundry areas commonly need at least one 20 amp branch circuit for laundry receptacle outlets, and NEC 210.8 requires GFCI protection in the listed laundry-area conditions.
Box fill is the NEC 314.16 volume check that counts insulated conductors, equipment grounding conductors, internal clamps, device yokes, and fittings. The legal calculation is separate from the physical problem: laundry boxes often contain 12 AWG copper, a bulky GFCI or tamper-resistant receptacle, a feed-through cable, and limited room behind a washer.
The practical workflow is to count the exact box before the wall is finished. A single 12/2 feed with one receptacle yoke may be easy. Add a downstream load cable or use the device as a GFCI feed-through point and the same box can move from comfortable to exact-limit.
Definitions to keep straight
A laundry branch circuit is the 20 amp dwelling circuit required by NEC 210.11(C)(2) for laundry receptacle outlets.
A device yoke is the strap or frame that supports the receptacle or GFCI device; under NEC 314.16(B)(4), it generally counts as two conductor allowances.
A conductor allowance is the cubic-inch value assigned by NEC Table 314.16(B), such as 2.25 cu.in. for each 12 AWG allowance.
IEC 60364 projects do not use NEC cubic-inch allowances directly, but the same design issue remains: conductor bends, terminal access, device depth, heat, and service space must be planned.
Five field rules for laundry boxes
Start with 12 AWG unless the design says otherwise
A 20A laundry branch circuit normally means 12 AWG copper, and each 12 AWG allowance is 2.25 cu.in. under NEC Table 314.16(B).
Count the GFCI or receptacle yoke
One device yoke on 12 AWG adds two allowances, or 4.50 cu.in., under NEC 314.16(B)(4).
Feed-through conductors change the box
A 12/2 feed plus a 12/2 load cable creates four insulated conductors before grounds, clamps, and the device yoke are counted.
Grounds count once, not zero
All equipment grounding conductors together count as one allowance based on the largest grounding conductor present under NEC 314.16(B)(5).
Do not let device depth be an afterthought
A box can pass at 18.00 cu.in. and still be hard to trim out when the GFCI body, washer hose clearance, and conductor folding all compete for space.
Laundry receptacle scenarios
These examples use NEC Table 314.16(B) values for 12 AWG conductors. Verify the marked box volume, adopted code edition, device listing, and local inspection requirements.
| Scenario | Counted items | Minimum volume | Practical box choice | Field note |
|---|---|---|---|---|
| Single 20A washer receptacle, one 12/2 feed, no internal clamp | 2 insulated conductors + grounds + one yoke = 5 allowances | 5 x 2.25 = 11.25 cu.in. | 15.0 cu.in. or larger | The math is simple, but device depth still matters. |
| Single 20A laundry GFCI, one 12/2 feed and internal clamp | 2 insulated conductors + grounds + clamp + yoke = 6 allowances | 13.50 cu.in. | 18.0 cu.in. deep box | A deep GFCI body makes the larger box worthwhile. |
| Laundry GFCI with line and load on 12 AWG | 4 insulated conductors + grounds + clamp + yoke = 8 allowances | 18.00 cu.in. | 20.0 to 22.5 cu.in. when available | This is the common exact-limit trap. |
| Two-gang laundry box with receptacle and switch | Often 6 insulated conductors + grounds + clamp + two yokes | Often 24.75 cu.in. or more | 4 in. square, 2-1/8 in. deep with cover | Two yokes on 12 AWG consume 9.00 cu.in. by themselves. |
| IEC-style utility room with 2.5 mm2 conductors | Use local enclosure-space rules, not NEC cubic inches | Local code calculation | Choose extra terminal and bend space | The NEC examples are planning checks, not imported law. |
Worked examples with specific numbers
Example 1: 12 AWG laundry GFCI with line and load
Assume one 12/2 cable feeds a laundry GFCI receptacle and one 12/2 cable leaves on the load terminals. Count four insulated 12 AWG conductors, one equipment-grounding allowance, one internal-clamp allowance, and one device yoke counted as two allowances. The total is 8 allowances. At 2.25 cu.in. per 12 AWG allowance, the minimum volume is 18.00 cu.in.
Example 2: washer receptacle protected by a GFCI breaker
If GFCI protection is supplied by a breaker and the box contains a standard receptacle with one 12/2 feed, the box-fill count can be smaller: two insulated conductors, one grounding allowance, and one yoke. Without an internal clamp, that is 5 allowances, or 11.25 cu.in. The device may be shallower, but NEC 210.8 protection still has to be verified.
Example 3: laundry receptacle plus light switch in a two-gang box
Suppose a two-gang laundry box has a 12/2 feed, a 12/2 cable continuing to the washer receptacle, a 12/2 switch leg for a nearby utility light, grounds, one internal clamp, one receptacle yoke, and one switch yoke. Six insulated conductors, one ground allowance, one clamp allowance, and four yoke allowances create 12 allowances. At 2.25 cu.in., the box needs 27.00 cu.in.
Code references to verify
Use these open references for background vocabulary, then verify the adopted code, product listing, manufacturer instructions, and authority having jurisdiction.
- National Electrical Code: Check NEC 210.11(C)(2), 210.52(F), 210.8, 314.16, 314.29, and 110.3(B) for laundry receptacle layout, GFCI protection, box fill, accessibility, and listed-use instructions.
- Residual-current device / GFCI background: Helpful background on shock-protection devices; apply the actual NEC GFCI rule and local amendments for laundry areas.
- American wire gauge: Useful for understanding why 12 AWG conductors require more cubic inches than 14 AWG conductors.
- IEC 60364: International readers should apply local IEC-based enclosure, terminal, and protective-device requirements rather than NEC cubic-inch values.
Laundry receptacle box-fill FAQ
How much box volume does a 12 AWG laundry GFCI with line and load need?
A common line/load GFCI layout with four insulated 12 AWG conductors, grounds, an internal clamp, and one yoke needs 8 allowances. At 2.25 cu.in. each, the minimum is 18.00 cu.in.
Does a GFCI breaker reduce box fill in the laundry receptacle box?
It can reduce physical device depth if a standard receptacle is used, but it does not remove the yoke count. One 12 AWG receptacle yoke still adds 4.50 cu.in. under NEC 314.16(B)(4).
Do laundry-area grounding conductors count separately?
No. Under NEC 314.16(B)(5), all equipment grounding conductors together count as one allowance based on the largest grounding conductor present.
Can a 15 cubic-inch box hold a feed-through laundry GFCI?
Usually no. A 12 AWG line/load GFCI with internal clamp commonly needs 18.00 cu.in., before adding any extra switch leg, second device, or oversized conductor.
How should IEC users apply this NEC guide?
Use the guide as a spacing checklist. IEC projects should verify local rules for 2.5 mm2 conductors, residual-current protection, terminal space, enclosure depth, and service access.
Technical note
Hommer Zhao reviews these guides from a conductor-packaging and termination-access perspective. Laundry boxes are a good example of why legal cubic inches and practical trim-out space should both be checked before drywall or cabinets limit access.
Check the laundry box before trim-out
Enter the final conductor size, conductor count, yokes, grounds, clamps, and fittings in the calculator before you commit to the laundry receptacle box.
Related calculator resources
Box Fill Calculator · GFCI Receptacle Box Fill Guide · Device Yoke Box Fill Guide · Wire Gauge Chart · NEC Code Reference