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.
| 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.
Frequently Asked Questions (FAQ)
What do I enter?
Total load in watts or amperes, then the voltage and circuit use, then press Calculate.
What does the result show?
The recommended MCB rating, the matching copper wire size, the breaker type, the load current, the design current with safety factor, and the breaking capacity.
Which MCB sizes are covered?
Standard ratings from 6 to 100 amps. Always choose the standard size above the design current, never below it.
What is the 125 percent safety factor?
If the load runs continuously for more than 3 hours, tick the checkbox and the tool multiplies the load current by 1.25 for the design current.
Can this replace an electrician?
No. The calculator is only a guide. Always have electrical work done by a qualified electrician, because a wrong breaker or wire can cause a fire.