What is the maximum volume for a standard 4-inch round box?

The maximum volume for a standard 4-inch round box is 21 cubic inches. This specification is based on the guidelines provided in the National Electrical Code (NEC), specifically in Article 314, which governs box fill calculations. The volume rating of a junction or outlet box is crucial because it determines how many conductors, devices, and fittings can be securely installed within that box without exceeding the safe limits.

In practice, the 4-inch round box is widely used in various electrical applications, and knowing that it has a 21 cubic inch capacity allows electricians to plan installations correctly and ensure compliance with the NEC. This capacity helps prevent overcrowding, which can lead to overheating and create safety hazards.

Understanding box fill requirements helps ensure that electrical installations are safe, functional, and up to code, which is essential for both new construction and renovations.