Fuse Size Calculator
Enter the appliance power in watts, the supply voltage and the type of fuse. The calculator works out the current and picks the right standard fuse rating.
- Watts to amps
- UK plug, car and glass
- Standard ratings
Check the appliance label and the cable rating. Never fit a fuse larger than the cable can carry.
A fuse should blow before the cable overheats, but not in normal use. The current an appliance draws is its watts divided by the voltage. A fuse rated a little above that current lets the appliance run normally and blows quickly if a fault sends the current much higher.
Fuse rating chart
Common appliances at 230 V. Search for an appliance.
| Appliance | Typical watts | Current (A) | UK plug fuse |
|---|---|---|---|
| Phone charger | 20 | 0.1 | 3 A |
| Lamp | 60 | 0.3 | 3 A |
| TV | 150 | 0.7 | 3 A |
| Desktop PC | 400 | 1.7 | 3 A |
| Fridge | 200 | 0.9 | 3 A or 13 A |
| Microwave | 1200 | 5.2 | 13 A |
| Hair dryer | 2000 | 8.7 | 13 A |
| Kettle | 3000 | 13 | 13 A |
| Washing machine | 2200 | 9.6 | 13 A |
UK plugs take only 3, 5 or 13 A fuses. Most appliances under 700 W should use 3 A, and larger ones 13 A.
Appliance power and plug fuse
UK 230 V plugs. Slide the power.
Fridges and freezers sometimes come with 13 A fuses because the compressor surges on start-up.
How to choose a fuse
Current first. Step through it.
Find the watts
On the appliance rating plate.
For car circuits, the fuse protects the wire. Match it to the wire gauge as well as the load.
Fast-blow or slow-blow
Two kinds of fuse. Compare them.
Breaks quickly on any overload. Protects sensitive electronics.
Rides through short start-up surges but still trips on faults.
Colour-coded plug-in fuses for 12 and 24 V circuits.
Never replace a slow-blow fuse with a fast-blow of the same rating on a motor. It will blow every time the motor starts.
Replacing a fuse safely
Quick checks. Tick each item.
Tick each item as you go.
If a new fuse blows straight away, there is a fault. Stop and have the appliance checked rather than fitting a bigger fuse.
What you get
Rating and reasoning. Each tile explains one result.
The standard size to fit.
Watts divided by volts.
Percent of the fuse rating.
Plug, blade or cartridge.
For car blade fuses.
Load on the fuse shows how close to its rating the appliance runs. Over 80% for long periods can cause nuisance blowing.
Frequently Asked Questions
No question matches that search.
What fuse do I need for 2,000 watts?
At 230 V that is 8.7 A, so a 13 A plug fuse. At 120 V, a 20 A fuse.
What fuse for a 1,000 W appliance?
4.3 A at 230 V. A 5 A or 13 A UK plug fuse.
How do I calculate fuse size?
Divide watts by volts for amps, add about 25% and round up to a standard rating.
What fuse for a 100 W device in a car?
100 ÷ 12 = 8.3 A. With 25% margin, a 15 A blade fuse.
Can I use a 13 A fuse instead of a 3 A?
It will work, but it will not protect a thin flex in a fault. Use the right rating.
What do the colours on car fuses mean?
Each rating has a colour: 10 A red, 15 A blue, 20 A yellow, 30 A green.
Why does my fuse keep blowing?
The appliance or cable has a fault, or the fuse is the wrong speed for a motor.
The right fuse every time
Turn watts into amps, add a margin and fit the next standard rating. Keep the fuse no bigger than the cable can take, and a blown fuse will always mean a fault worth checking.
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