Estimate fuse size from load amps, watts, voltage, phase type, continuous load factor, safety factor, and motor or startup factor. This calculator helps with basic fuse amperage and circuit protection planning.
Load amps:
The calculator uses entered amps or converts watts or volt-amps into amps based on voltage, phase type, and power factor.
Adjusted fuse amps:
Continuous load, startup, and safety factors are applied to estimate fuse amperage.
Fuse size:
The adjusted amperage is rounded up to the next common fuse size for planning.
A fuse size calculator helps estimate the fuse amperage needed to protect a circuit or piece of equipment.
It can help with DC circuits, battery circuits, solar wiring, motors, transformers, appliances, lighting, electronics, equipment panels, and general electrical planning.
Your result shows recommended fuse size, calculated load amps, adjusted fuse amps, fuse load percentage, estimated watts, volt-amps, estimated wire size, voltage, phase type, and comparison scenarios.
Estimate the load current, apply any required continuous or startup factor, then choose a fuse size that matches the circuit, conductor, equipment, and fuse type requirements.
Usually the fuse must be large enough to carry normal current but small enough to protect the wire and equipment. Continuous and startup loads may require extra sizing review.
Fast-acting fuses open quickly during overcurrent. Time-delay fuses can tolerate brief inrush current, which is often useful for motors, transformers, and compressors.
No. This is a simplified planning tool. Always verify fuse class, voltage rating, interrupt rating, AC/DC rating, conductor size, equipment instructions, and local electrical code with a qualified electrician.