Box Fill Calculator
Conductor Size/Number
18 AWG = 0
16 AWG = 0
14 AWG = 0
12 AWG = 0
10 AWG = 0
8 AWG = 0
6 AWG = 0
Devices
Device 1 = 0
Device 2 = 0
Device 3 = 0
Device 4 = 0
Device 5 = 0
Device 6 = 0
Other
Clamps = 1
Fixture Studs = 1
Hickeys = 1
Largest Ground = 0
Largest Isolated Ground = 0
CV =
DV =
CLV =
FSV =
HSV =
GV =
IGV =
Volume [test - in^3] =
Volume =
awg_total =
awg_sum =
awg_largest =
Help
Calculates the minimum volume required for junction and outlet boxes containing 6 AWG and smaller conductors. These calculations are based on the 2014 National Electrical Code requirements and take into consideration all contained conductors and other fittings and devices. Enter the number and size of conductors contained in the box to calculate the minimum volume required for the box.
Rows
Conductor Size/Number
Enter the number of ungrounded (hots) and grounded (neutrals) for each size of conductor contained within the box. Do not include equipment grounding conductors (grounds) in this section. If unspliced conductors pass through the box in lengths longer than 12 inches, each of these conductors must be counted twice. For example: If 3- 12 AWG conductors are coiled in a box in 12 inch or greater lengths and pass through the box without splice or termination, the conductors must be counted twice and 6 would be entered into the 12 AWG section. Do not enter a number for a conductor size if that size conductor is not present in the box.
- 18 AWG:
- 16 AWG:
- 14 AWG:
- 12 AWG:
- 10 AWG:
- 8 AWG:
- 6 AWG:
Devices
Select the conductor size that corresponds to the largest conductor connected to the device
that is present in the box. For example: If 2 switches are installed in a box and 1 is connected to 14 AWG conductors and the other is connected to 12 AWG conductors, select 14 AWG for Device 1 and 12 AWG for Device 2. Selections should only be made for the number of devices installed in the box. All other entries should be left blank. If a large device is installed in a box that requires more than 1 gang for mounting, a selection must be made for each gang required for mounting the device. For example: If a
50 amp range receptacle were installed in a 2 gang box and connected to 6 AWG conductors, select 6 AWG for Device 1 and 6 AWG for Device 2.
- Device 1:
- Device 2:
- Device 3:
- Device 4:
- Device 5:
- Device 6:
Other
- Clamps: Select whether the box contains internal cable clamps. Internal cable clamps are those where the clamping mechanisms are inside of the box. Cable clamps whose clamping mechanisms are outside of the box do not need to be counted.
- Fixture Studs: Select whether the box contains lighting fixture studs.
- Largest Ground: Select the largest equipment grounding conductor present in the box. If no equipment grounding conductors are in the box, leave this selection blank.
- Hickey: Select whether the box contains a hickey. Hickeys are commonly used for the support of heavy lighting fixtures.
- Largest Isolated Ground: Select the largest isolated equipment grounding conductor present in the box. If no isolated equipment grounding conductors are present in the box, leave this section blank. Isolated grounding type receptacle outlets are identified by an orange triangle on their face and are provided with 2 sets of equipment grounding conductors that remain separated within the outlet box. One set of grounding conductors is used for grounding the outlet box and the other set of grounding conductors is used for grounding the receptacle outlet. The NEC requires that the largest equipment grounding conductor in each set be counted for box fill purposes.
- Volume: Volume allowed for the box.
Examples
Calculate the minimum volume required for a box that contains six- 12 AWG conductors and a 12 AWG grounding conductor. This box also contains internal cable clamps and the 12 AWG conductors are connected to a receptacle outlet.
Conductor Size/Number
- 18 AWG: 0
- 16 AWG: 0
- 14 AWG: 0
- 12 AWG: 6
- 10 AWG: 0
- 8 AWG: 0
- 6 AWG: 0
Devices
- Device 1: 12 AWG
- Device 2: ---
- Device 3: ---
- Device 4: ---
- Device 5: ---
- Device 6: ---
Other
- Clamps: Yes
- Fixture Studs: No
- Hickey: No
- Largest Ground: 12 AWG
- Largest Isolated Ground: ---
The minimum volume required for this box is 22.5in³.
Keywords
18 AWG
16 AWG
14 AWG
12 AWG
10 AWG
8 AWG
6 AWG
Device 1
Device 2
Device 3
Device 4
Device 5
Device 6
Clamps
Fixture Studs
Hickeys
Largest Ground
Largest Isolated Ground
Volume
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