Garages

I have yet to bother fully wiring my shed as all the tools I have been using have nowhere near troubled the 13A socket the extension lead is plugged into (mitre saw, pillar drill, track saw, belt sander etc - not all at once but usually singularly in combo with a shop vac, lights and battery chargers).

Shed is wired internally with 4 double sockets on a ring main (16A RCD), and two LED strip lights on their own 6A RCD. The CU "tail" then plugs into the extension lead when I want power.

You'd have to be going some to overload a 13A socket if you're only running one tool at a time. Unless you're running a 2/3kw heater plus tools, then you could manage it fairly easily.

Easy to work out.

Current (Amps) = Watts of whatever you're powering / Voltage (nominally 230 in the UK, often closer to 240 but safer to use 230 for calcs)

e.g. a 3kw heater = 3000 Watts / 230 Volts = 13Amp

This is why you'll never see anything over 3kw with a domestic 13A plug on it, and why things like kettles and immersion heaters are very often 3kw, or close to it.

So if you had a 1500w table saw and a 1000w extractor, you'd still be comfortably under the 13A, but you might find the spike from the table saw starting up is enough to trip an MCB/RCBO.