Enter your load's current or wattage to find the correct breaker size, using the standard 125% continuous-load safety margin.
This follows the standard NEC 210.19/210.20 practice of sizing continuous-load circuits at 125% of the load — always confirm against your local code and have electrical work done by a licensed electrician.
A circuit breaker protects the wire behind it from overheating, so its rating needs to account for how long a load actually runs — a continuous load (anything running 3 hours or more, like an EV charger or built-in lighting circuit) requires 25% extra headroom under standard electrical code practice, while a short-duration load doesn't. Once you have the required minimum, round up to the nearest standard breaker size (15, 20, 25, 30, 40, 50A, and so on) — never round down. Pair this with the wire gauge calculator to confirm your wire is rated for the same breaker size.
Continuous loads run long enough to build up sustained heat in the wire and breaker, so codes require 25% extra capacity as a safety margin — a non-continuous, short-duration load doesn't need that same margin.
No — always round up to the next standard size at or above the calculated minimum; rounding down undersizes the protection for that circuit.