In article ,
"soup" writes:

Does anyone have a favourite site, to work out the CSA required for a
piece of cable, basically I want to make up an extension to run a

General guideline for extension leads fused at 13A...
1.25mm² up to 12m long
1.5mm² up to 15m long
2.5mm² up to 25m long (2.5mm² flex won't easily fit in a 13A plug).
These come from the PAT testing recommendations, with the earth
fault loop impedance being the limiting factor.

Lengths can be increased with a proportional reduction in the value of
plug fuse value fitted in the extension lead, e.g. with a 5A fuse fitted,
31m, 39m, and 65m respectively for the three cable sizes above.

circular saw (1200 W) [at 240V that is 5A] asked the chap in the local
Hardware shop for cable large enough to deal with 2 kilowatt (mmm over
speccing as usual), he said he had nothing that could deal with that
much power 2k was "cooker sized", but my kettle (e.g.) is 2200 W, so
can't trust him as far as I can throw him.

--
Andrew Gabriel