Circuit Breaker Size Calculator
Size your circuit breaker correctly the first time. Enter the total load and voltage, then get the recommended MCB rating, suitable wire size and breaker type - essential for safe home wiring and solar installations.
Safety: This calculator is only a guide. Always have electrical work done by a qualified electrician — a wrong breaker or wire can cause a fire.
Applies to the watts option.
Recommended MCB
—
Breaker type
—
| Load current | — |
|---|---|
| Design current (with safety factor) | — |
| Recommended copper wire | — |
| Breaking capacity | 6 kA (home) / 10 kA (commercial) — should be printed on the breaker |
Standard MCB sizes
6A · 10A · 16A · 20A · 25A · 32A · 40A · 50A · 63A — always choose the standard size above the design current, never below it.
How to use
- Enter total load in watts or amperes.
- Select the voltage and circuit use.
- Press Calculate — see the recommended MCB, wire size and type.
Tips
- Always round the breaker size up to the next standard rating - never down.
- Add a safety margin: continuous loads should not exceed 80 percent of the breaker rating.
- Match the wire size to the breaker - an oversized breaker on thin wire is a fire risk.
- For solar or inverter circuits, use the setting that matches your actual circuit.