How to Calculate Circuit Breaker Size Easily – Online Electrical Tool

10/23/2025

Correctly sizing a circuit breaker is crucial for electrical safety and efficient energy distribution. Our free Circuit Breaker Size Calculator allows electricians, engineers, and students to quickly determine the appropriate breaker size based on load current and system voltage.

When is it useful?

• Designing home or office electrical panels
• Selecting breakers for specific equipment (e.g., soldering stations, UPS, compressors)
• Replacing an old breaker and ensuring proper protection and performance

Example: How to Calculate Breaker Size for a Refrigerator

Step 1: Gather Refrigerator Specifications

A standard household refrigerator (e.g., 20–25 cu. ft.) typically has:

• Power Consumption: around 600 watts
• Voltage: in the U.S. — 120 V
• Current Type: Single-phase
• Safety Factor: recommended 1.25–1.5 to account for compressor startup current

Step 2: Enter the Data in the Calculator

• Voltage: 120
• Power: 600
• Safety Factor: 1.25 (or up to 1.5 for older refrigerators)
• System Type: Single-phase

Result:

So, a 10-amp circuit breaker is suitable for a dedicated refrigerator line — which is standard for residential use in Florida.

Conclusion:

A 10A breaker is generally sufficient for a refrigerator.
If the same circuit powers other devices like a microwave or countertop outlet, a 15A breaker may be necessary.
Always consider inrush current from the compressor — especially on older models. In such cases, a 15A slow-blow breaker is a safer choice.

Need the right breaker size?
Try our new online Circuit Breaker Size Calculator
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