Calculator

Socket Load Calculator

Check if you are overloading a socket or extension lead. Select the appliances plugged in to see the total wattage and whether it is safe.

How to Use

Toggle on each appliance that is plugged into the same socket or extension lead.

Check the total wattage against the 3,000W maximum for a standard UK 13A socket.

If the status shows 'Warning' or 'Danger', unplug high-wattage appliances and spread them across different sockets.

Never plug one extension lead into another (daisy-chaining) as this increases fire risk.

About This Calculator

This socket load calculator helps you check whether the combination of appliances plugged into a single socket or extension lead exceeds the safe limit. A standard UK 13A socket can handle up to 3,000 watts. Overloading sockets is one of the leading causes of electrical fires in the UK — use this tool to check before you plug in.

Frequently Asked Questions

What is the maximum wattage for a UK socket?

A standard UK 13A socket can safely handle up to 3,000 watts (13 amps x 230 volts = 2,990W, rounded to 3,000W). This applies to both wall sockets and extension leads. Exceeding this limit risks overheating the wiring, melting the socket, or starting a fire.

Can I use a 4-way extension lead safely?

Yes, but the total load across all sockets on the extension must not exceed 3,000W (13A). A common mistake is assuming each socket on a 4-way lead can handle 3,000W — it cannot. The entire lead shares one 13A fuse. Low-wattage devices like phone chargers and lamps are fine, but never plug in two high-wattage appliances like a kettle and a heater.

What are the signs of an overloaded socket?

Warning signs include: hot plugs or sockets, scorch marks or discolouration around the socket, a burning smell, flickering lights, or blown fuses / tripped circuit breakers. If you notice any of these, unplug everything immediately and have an electrician inspect the socket.

Is it safe to plug a heater into an extension lead?

It is best avoided. Fan heaters draw up to 3,000W — the entire capacity of the extension lead. If anything else is plugged into the same lead, you will exceed the safe limit. Plug heaters directly into a wall socket and make sure nothing else is on the same double socket.

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