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Interactive calculator

Breaker sizing calculator

Estimate a standard breaker size while keeping the load, continuous-duty margin, and conductor coordination visible.

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1Tell us what you knowUse the simple fields first.
2See the recommendationSolarLab explains what the number means.
3Refine or downloadContinue only when the result makes sense.

Inputs

i
Voltage of the protected circuit. Example: 51.2 V nominal for a 48 V-class LiFePO4 battery circuit, or 230 V AC.
i
Total equipment power connected to the circuit. Example: 3000 W inverter load.
i
Enter current directly when known. The calculator uses the higher of entered current or watts divided by voltage.
i
A continuous load runs for a long period. A larger design margin is usually required.
Visual aid

Protection device visual

SOLARLAB
MCB / DC BREAKER
Breaker purpose

A breaker disconnects the circuit when current becomes unsafe. It must protect the cable and match the circuit voltage and fault-current requirements.

Example

Example calculation

SolarLab uses the current project values to show how the recommendation changes.

Common mistake

Do not rely on one number alone

Check the result against actual equipment and site conditions.

Frequently asked

Is this installation-ready?

No. It is a planning estimate that should be verified by qualified professionals.

How was this calculated?

Calculation method

Formula

The calculator uses the displayed inputs and standard planning relationships.

Important assumptions

Verify the final design against actual equipment data sheets, site conditions, and applicable requirements.

Read the full methodology and update history →
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