Ampton
Add up everything plugged into one wall socket or extension lead, and see if it's within the limit or heading for an overload.
Nothing on the lead. Add an appliance above.
How it reads
A UK wall socket, plug fuse and most extension leads are rated 13 amps, which at 230 volts is about 3,000 watts. The catch is that a four-way lead is 13 amps for the whole lead, not per socket, so four plugs don't give you four times the power. Ampton adds the wattage of everything on the lead, converts it to amps, and shows how much of the rating you've used.
High-power heating appliances — kettles, heaters, irons, washing machines, tumble dryers — each take a big share and run hot, so they're safest in a wall socket on their own rather than shared on a lead. And never plug one extension lead into another: all the current runs through the first lead's 13 amps.
Wattages shown are typical. The real figure is on the appliance's rating plate; type it in to be exact. Figures follow Electrical Safety First's overloading-sockets guidance and the BS 1363 13-amp rating for UK plugs and sockets.
Ampton is a guide for everyday appliances, not a substitute for an electrician. If a socket or plug feels hot, is scorched, or a breaker keeps tripping, stop using it and get it checked.