4" Octagon Box 1-1/2" Deep
Standard 4-inch octagon electrical box with 1-1/2 inch depth. Popular choice for ceiling mounted fixtures and junction points.
15.5
cu.in. Volume
7
Max 14 AWG
6
Max 12 AWG
4" Octagon x 1-1/2"
Dimensions
Conductor Capacity per NEC 314.16
Maximum number of conductors that can fit in this 15.5 cu.in. box based on wire gauge (not accounting for devices, clamps, or grounds).
| Wire Gauge | Volume Each | Max Conductors* |
|---|---|---|
| 18 AWG | 1.5 cu.in. | 10 |
| 16 AWG | 1.75 cu.in. | 8 |
| 14 AWG | 2 cu.in. | 7 |
| 12 AWG | 2.25 cu.in. | 6 |
| 10 AWG | 2.5 cu.in. | 6 |
| 8 AWG | 3 cu.in. | 5 |
| 6 AWG | 5 cu.in. | 3 |
*Theoretical maximum for conductors only. Actual capacity will be less when including devices, clamps, and grounding conductors.
Common Applications
Calculate Box Fill for 4" Octagon Box 1-1/2" Deep
Use our free calculator to verify your 4" Octagon Box 1-1/2" Deep meets NEC 314.16 requirements.
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About the 4" Octagon Box 1-1/2" Deep
The 4" Octagon Box 1-1/2" Deep provides 15.5 cubic inches of volume for electrical connections. This metal box is commonly used for ceiling light fixtures, ceiling fans, junction boxes, smoke detector mounting. With dimensions of 4" Octagon x 1-1/2", it offers adequate space for most residential and light commercial applications.
Box Fill Calculation Example
For a typical installation using 14 AWG conductors:
- Box volume: 15.5 cu.in.
- 14 AWG conductor volume: 2.00 cu.in. each
- Maximum conductors (theoretical): 7
Remember to account for devices (2× conductor volume each), internal clamps (1× conductor volume), and equipment grounding conductors (1× conductor volume for all grounds combined).
Practical Example: Receptacle Installation
Installing a duplex receptacle with two 14/2 NM cables in this box:
- 4 × 14 AWG conductors = 4 × 2.00 = 8.00 cu.in.
- 2 × grounds (count as 1) = 1 × 2.00 = 2.00 cu.in.
- Internal clamps = 1 × 2.00 = 2.00 cu.in.
- 1 × receptacle = 2 × 2.00 = 4.00 cu.in.
- Total: 16.00 cu.in.
Result: 16.00 cu.in. > 15.5 cu.in. = NOT COMPLIANT - Use larger box
Related Resources
- Complete NEC 314.16 Guide
- How to Calculate Box Fill Step-by-Step
- Junction Box Sizing Guide
- Wire Gauge Volume Chart
- NEC 314.16 Code Reference
Need Help with Box Fill?
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