Extension lead and socket load calculator
Gaming setups add up quickly: a PC, two monitors, speakers, a charger and more. Enter what is plugged into one lead and see whether it is within the rating printed on the lead.
How to check the load on a lead
Every extension lead and socket has a maximum rating, printed on the product. In the UK a standard plug and socket is rated at 13 amps, and at 230 volts that corresponds to about 2,990 watts. Every device you plug in draws part of that. Add up the real draw of your PC, monitors and accessories and compare the total with the rating of the lead.
The calculator does the sum for you and shows the load as a share of the rating. A gaming PC with two monitors and a few extras typically uses around 600 watts, far below a 13 amp lead's capacity, but combining it with a heater or a second PC changes the picture quickly.
Common ratings and what they allow
At 230 volts, each amp of rating allows 230 watts. Always read the label on your own lead.
| Rating | Maximum power | At 80 percent |
|---|---|---|
| 3 A | 690 W | 552 W |
| 6 A | 1,380 W | 1,104 W |
| 10 A | 2,300 W | 1,840 W |
| 13 A | 2,990 W | 2,392 W |
Why a margin below the maximum matters
The rating is the most a lead can deliver without overheating, not a comfortable everyday figure. Plugs, sockets and thin cables warm up when they carry a heavy load for hours, and many guides suggest keeping continuous loads well below the rating. This tool uses 80 percent as a default margin, which you can change, and shows how many watts that leaves for the setup.
Power draw is also higher than idle figures suggest. A graphics card in a heavy game can add several hundred watts in a second. Use the PSU wattage calculator to estimate the peak, and the UPS runtime calculator if you add a battery backup.
Cable reels, surge protectors and good habits
Cable reels need special care. A reel that is coiled can overheat, so manufacturers often give two ratings: a lower one when coiled and a higher one when fully unwound. Always unwind the cable fully if you use a reel. Surge protectors guard against voltage spikes but do not raise the current rating, so the total load must still fit the lead.
Avoid chaining extension leads, never overload a single socket, and replace leads that are warm, discoloured or damaged. If you are unsure about your wiring, ask a qualified electrician. The figures here are general information, not a safety certification. To see what your setup costs to run, use the electricity cost calculator.
How to use the extension lead load calculator
- Read the rating label on your extension lead or the socket in amps.
- Enter your PC power under load from the PSU wattage calculator or a plug-in meter.
- Add monitors and every other device on the same lead.
- Leave the recommended share at 80 percent unless the maker says otherwise.
- If the load is high, move devices to a second lead or socket.
Common mistakes to avoid
- Plugging in a heater or kettle alongside the PC.
- Using a coiled cable reel without checking its coiled rating.
- Chaining extension leads together, which can overload the first one.
Related tools and guides
Keep going with these: PSU wattage calculator, UPS runtime calculator, electricity cost calculator, PSU efficiency calculator, 1000W to 1300W PSU guide.
Frequently asked questions
How many watts can a 13 amp extension lead handle?
At 230 volts a 13 amp lead is rated for about 2,990 watts, but the label on your lead is what counts. Cable reels are often rated lower when coiled. For continuous loads many guides suggest staying near 80 percent of the rating.
Can I plug a gaming PC and monitors into one extension lead?
Usually yes. A gaming PC, two monitors and small accessories often use well under 1,000 watts, which is within a 13 amp lead. Check your total with this tool and avoid adding high-power items such as heaters to the same lead.
Is it safe to daisy chain extension leads?
It is best avoided. Chaining leads can overload the first lead and adds more plugs that can overheat. Use one lead that is long enough, with a rating that covers the load, or add another wall socket if you need more outlets.
What is the difference between a surge protector and an extension lead?
An extension lead adds sockets. A surge protector also contains parts that guard against voltage spikes. Neither raises the current rating, so the total load still has to fit within the amp rating of the product. Check the label on both before you buy.
Does my PC draw its power supply wattage all the time?
No. A power supply label shows maximum capacity. A PC draws far less when idle and varies with the game. Use the real load from a plug-in power meter or the PSU wattage calculator when checking an extension lead. It gives a far more realistic answer.
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