United States calculator
Plan a U.S. fuse size from load and conductor limits
Estimate a standard U.S. fuse size from load current, continuous-load treatment and conductor ampacity while clearly flagging combinations that require redesign.
Continuous-load factor and standard sizes
Calculator inputs
Fuse Size Planning Calculator results
How this Fuse Size Planning Calculator works
A continuous load is multiplied by 125% for this planning reference. The calculator selects the smallest standard fuse at or above the resulting current without exceeding the entered conductor ampacity.
Important: This is not electrical design approval. Motor, HVAC, photovoltaic, battery, transformer and appliance circuits can have special rules. Use equipment instructions and a qualified professional.
What assumptions should I verify?
Verify every entered quantity, rate, unit, product specification and local requirement before relying on the estimate. U.S. conventions are primary where location matters.
Is information sent anywhere?
No. Calculations run locally in the browser and this calculator sends no entered information to a remote service.