Burning Electrical Wire

Calculate The Correct Fuse Size For Your Project

What is a electrical fuse & do I need one in my circuit?

A fuse protects an electrical circuit from overloads. It is a safety feature designed to protect expensive equipment and stop electrical fires. In the event of a short circuit the fuse blows cutting power and stopping wires melting. Using the correct fuse is important because a undersized fuse can stop circuits operating by cutting power at low currents. An over-sized fuse will allow too much current to flow. This defeats the purpose of using a fuse as a safety device.

Select a fuse In three simple steps

Things can get ugly fast! To avoid melted wires and damaged components its important to select the right fuse with these steps and the calculator below.

  1. Identify the load current in the circuit. See this guide to learn how to calculate load current.
  2. Identify the smallest gauge wire the load current will flow through.
  3. Enter values in the calculator below

One common misconception about choosing the correct fuse size is that it depends on the load of the circuit. However, the load of the circuit is not suitable to use alone when choosing a fuse size. The fuse size should be based on the SMALLEST wire in the circuit.

Accounting For Temperature

Fuses ratings are accurate for operation at 25 Degrees Celsius, When subjected to hotter or colder environments the fuse material will blow at a difference temperature. This effect is minimal for most normal temperatures from 0-50 Degrees Celsius. When outside this range It is important to also take this into consideration for your wiring choices particularly when temperature are hot.



All electrical systems present a risk of fire and other hazards. Fuse Factory makes no representation or warranty that this calculator will be suitable to address your particular situation or requirements.

Fuse Factory has developed this calculator for use only by individuals having the appropriate working knowledge and understanding of electrical systems. The Calculator is based on Industry standards including E-11 “AC and DC Electrical Systems on Boats,”. It it is not a substitute for calculations based directly on these or other industry standards that may apply. These calculators are prototypes, and may contain errors of entry or calculation.

These calculators can not account for all possible circumstances, factors or variables pertinent to the selection of an appropriate wire and circuit protecting fuse. These variables could include adding additional loads to circuits, Inadequate or defective insulation, Software malfunctions of a browser or server computer, data import errors, environmental heat sources, Heated terminations such as fixtures and fuse blocks.

This calculator is not a replacement for the expertise of a electrical professional. Under no circumstances should this calculator be the only resource for selecting wire size or circuit protection. Any wire size or circuit protection recommended by this calculator should be reviewed for adequacy, before installation, by a professional applying the applicable industry standards.

Fuse Factory expressly disclaims responsibility for any use of this calculator that results in inadequate wire size or circuit protection.

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  1. I am going to have 2x250w solar panels wired in series with a combined voltage of 80vdc and 9amp going through a 8AWG wire to a charge controller. My query is are maxi fuses able to have 80vdc going through them, or are they limited to 12/24vdc? Cheers.

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