Free 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.
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.
Results
Fill in the details and select Calculate to see your figures.
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Get a free demoHow to use the Socket Load Calculator
- 1Toggle on each appliance that is plugged into the same socket or extension lead.
- 2Check the total wattage against the 3,000W maximum for a standard UK 13A socket.
- 3If the status shows 'Warning' or 'Danger', unplug high-wattage appliances and spread them across different sockets.
- 4Never plug one extension lead into another (daisy-chaining) as this increases fire risk.
How to work it out yourself
The safe limit of a socket or extension lead is set by current (amps), not wattage directly. Convert each appliance's wattage to the current it draws at the UK mains voltage of 230 V, add them up, and compare against the fuse rating.
- Kettle 3,000 W ÷ 230 V = 13.0 A: on its own it already uses the full 13 A fuse.
- Hair dryer 2,200 W ÷ 230 V = 9.6 A, plus a fan heater 3,000 W ÷ 230 V = 13.0 A → 22.6 A combined.
- 22.6 A is well over the 13 A fuse in a single socket or 4-way lead, so that combination is unsafe.
- Low-power items are fine: a 60 W lamp draws 0.26 A and a 5 W charger draws 0.02 A.
This is the socket/extension-lead limit (one 13 A BS 1363 fuse). It is separate from the circuit behind the wall: a ring final circuit is protected at 32 A and a radial at 20 A or 32 A, and BS 7671 applies diversity (an allowance that not every point runs at full load at once) when designing those circuits. This tool only checks a single socket outlet. If you are sizing a circuit, use a qualified electrician.
Typical UK benchmarks
| UK Socket Limit (13A) | 3,000W max, BS 1363 |
| Extension Lead Limit | Most 4-way leads rated at 13A / 3,000W, same BS 1363 fuse rating |
Disclaimer
This tool gives an estimate for general guidance only, based on typical UK figures and the details you enter. It is not a formal quote, survey, or professional advice. Always confirm with a qualified tradesperson before relying on any figure, as regional prices, site conditions, and current standards vary.
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Get a free demoFrequently 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.
Does overloading a socket mean my wiring is unsafe?
Not necessarily. A single overloaded lead is usually a usage problem, not a wiring fault. But if sockets feel warm in normal use, breakers trip often, or the installation is old, the fixed wiring itself may be at fault. A modern consumer unit under BS 7671 (the IET Wiring Regulations) should include RCD protection that trips on a fault. If in doubt, an EICR by a registered electrician will confirm whether the wiring is safe.
