The size of the fuse in a plug depends on the electrical current that the appliance or device is rated to use. In the United Kingdom, the standard sizes for fuses in plugs are 3amp, 5amp, 13amp, and 15 amp. It is important to use the correct size fuse for the appliance or device, as using a fuse that is too small can cause the fuse to blow frequently, while using a fuse that is too large can increase the risk of an electrical fire.

To determine the correct size fuse for your appliance or device, you can check the manufacturer's documentation or the label on the appliance itself. The documentation should specify the maximum current rating for the appliance, which will indicate the size of the fuse that should be used. If you are unable to find this information, you can use the following general guidelines to select the appropriate fuse size for appliances use:

  • less than 750 watts of power - 3amp fuse 
  • between 750 and 1000 watts of power - 5amp fuse
  • between 1000 and 3000 watts of power, a 13amp fuse
  • more than 3000 watts of power, a 15amp fuse

Keep in mind that these are general guidelines and may not apply to all appliances. It is always best to check the manufacturer's documentation or label to determine the correct size fuse for your specific appliance.