Estimate a reference breaker size from separate continuous and noncontinuous loads using the 125% continuous-load planning factor.
Calculator
Breaker Planning Result
Review the main result, supporting measurements, and calculation details.
Load and Capacity Analysis
Calculation Details
| Metric | Value | Note |
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How to estimate breaker size
Enter continuous load separately from noncontinuous load. The calculator applies 125% to the continuous portion, adds the noncontinuous portion, and selects the next standard breaker rating at or above that planning current.
minimum planning current = 125% x continuous load + noncontinuous load
Breaker-size example
A 16 A continuous load with no other load produces 20 A of planning current, so the reference result is a 20 A breaker. A 16 A continuous load plus 5 A noncontinuous load produces 25 A.
Why continuous load is treated differently
NFPA material for Article 215 describes feeder sizing for a combination of noncontinuous load plus 125% of continuous load, subject to listed 100%-rated assemblies and other exceptions. A continuous load is generally one expected to remain at maximum current for three hours or more.
A breaker does not size the whole circuit
The selected overcurrent device must protect conductors and match equipment, terminal, fault-current, panel, and local requirements. Some loads such as motors, HVAC, welders, and EV supply equipment use additional rules or nameplate values. Confirm the complete circuit with a licensed electrician and the AHJ.
Frequently asked questions
Is the next standard size always allowed?
No. This tool rounds to a familiar rating for planning, but conductor and equipment rules can prohibit that result.
Can I add every appliance breaker to size a panel?
No. The US Department of Energy notes that panel breakers cannot simply be added because not every load operates simultaneously. Residential service calculations use specific demand methods.
What wire size goes with the result?
Use the wire size calculator for a preliminary conductor check, then verify the installation professionally.