Advice given here is based on information and guidance provided in the IET Code of Practice (5th Edition).

Fixing Factory assumes no liability for the use of this calculator.

Source code for this calculator can be found here.

Older equipment might not comply with these recommendations.

Formerly a 3 amp fuse was recommended for cables with CSA of 0.5 mm² and a 13 amp fuse in larger cables.
(There was an exception, as now, for equipment with a cable of CSA 0.5 mm² and high inrush current, where a 5 amp fuse was permitted.)

It is not necessary to alter fusing that complied with recommendations at the time of manufacture.