2 gang electrical box dimensions
The following are the common size specifications of the **2 Gang Electrical Box**, covering **indoor standard types**
and **underground/concrete-specific types**, and accompanied by **industry standards** and **purchase suggestions**:
I. Sizes of Indoor Standard 2 Gang Electrical Boxes (Mainstream Scenarios)
They are suitable for the installation on the walls/ceilings of residential and commercial buildings. The materials are mainly
**plastic** or **metal**, and they comply with the **NEC (National Electrical Code in the United States)** or **GB 7251
(Chinese National Standard)**.
1. Plastic 2 Gang Boxes (Mainstream Models)
| Type | Size (inches) | Depth (inches) | Features | Suitable Equipment |
| 2x4 2 Gang Box | 4.875 (Length) × 3.875 (Width) | 1.5 / 2.0 / 2.5 | Lightweight, flame-retardant, corrosion-resistant | Double switches, double sockets, sound and light control panels |
| 3x2 2 Gang Box | 3.5 (Length) × 2.25 (Width) 3.5×2.25 | 2.0 / 2.5 | Compact, suitable for thin walls | Small double-control switches, network panels |
#### 2. Metal 2 Gang Boxes (Explosion-proof/Industrial Scenarios)
| Type | Size (inches) | Depth (inches) | Material | Special Design |
| Square 2 Gang Box | 4.5 × 4.5 | 2.0 / 3.0 | Hot-dip galvanized steel plate | Can be grounded, explosion-proof certification (such as ATEX) |
| Octagonal 2 Gang Box | 4.75 (Diameter) | 2.0 / 2.5 | Aluminum alloy | Sprayed plastic on the surface, anti-oxidation |
3. Key Installation Parameters
- **Distance between Screw Holes**: 3.1 inches (suitable for standard double-device panels);
- **Knockout Hole on the Back**: 0.625 inches in diameter (suitable for 1/2" electrical conduits);
- **Volume Requirement**: The NEC stipulates that the minimum volume of a 2 gang box is **22 cubic inches**
(approximately 360 cubic centimeters).
II. Sizes of Underground/Concrete-specific 2 Gang Electrical Junction Boxes
They are suitable for scenarios such as buried in the ground and concrete pouring, emphasizing **waterproofing
and compression resistance**, referring to **GB 50169 (Grounding Specification)** and **IP Protection Rating**.
1. Concrete 2 Gang Boxes (Municipal/Civil Air Defense Projects)
| Brand | Model | Size (inches) | Protection Rating | Features |
| Oldcastle | 2x4 CPB Double | 24 (Length) × 12 (Width) × 24 (Depth) | IP66 | Prefabricated concrete, stackable and expandable |
| Siemens | SIC800-2G | 10 (Length) × 8 (Width) × 10 (Depth) | IP67 | Built-in waterproof rubber ring, supports cable branching |
2. Plastic 2 Gang Boxes (Damp Environments)
| Model “Model | Size (mm) | Depth (mm) | Material | Application |
| Carlon 2G | 124 (Length) × 98 (Width) | 38 / 50 | Reinforced PVC | Wiring of buried sensors |
III. Size Unit Conversion and Precautions
1. **Inches → Centimeters**: 1 inch = 2.54 centimeters (Example: 4.875 inches ≈ 12.4 cm);
2. **Depth Selection**:
- For Ordinary Walls: **1.5~2.0 inches** (suitable for 86-type panels);
- For Thick Walls or with Many Cables: **2.5~3.0 inches** (deep boxes);
3. **Pre-embedding in Concrete**: It is necessary to reserve a **settlement allowance of 1~2 cm** to avoid insufficient
elevation after pouring.
IV. Purchase Suggestions
1. **Indoor Scenarios**:
- Give priority to choosing **plastic 2 gang boxes** (such as Leviton R5200-W), which are low in cost and easy to install;
- Metal boxes need to be equipped with **insulating gaskets** to prevent short circuits.
2. **Underground Scenarios**:
- Use **concrete 2 gang boxes** (Oldcastle) in load-bearing areas, and **IP68 plastic boxes** (Tangshan Pingsheng
DATA-E02G) in non-load-bearing areas;
- Check the **sealing grade** to ensure that the cover plate is equipped with a **silicone ring** or **epoxy resin potting**.
3. **Special Requirements**:
- Choose **ATEX-certified metal boxes** (such as Raco 6500) for explosion-proof sites;
- Choose **transparent plastic boxes** (such as Hubbell 5060C) if maintenance markings are required.
V. Conclusion
The size of the 2 gang electrical box needs to be selected according to the **application scenario** (indoor/underground),
**material** (plastic/metal/concrete), and **equipment type** (switch/socket/sensor). The indoor standard boxes are mainly
**4.875×3.875 inches**, and the underground boxes need to be customized as large-sized and compression-resistant models.
At the same time, pay attention to the protection rating and the reserved amount for installation.
