- P
- Power: the appliance's rating in watts (W), on its plate or label. 1 kW = 1,000 W
- V
- Voltage: the supply in volts (V), such as 230 V mains or a 12 V battery
- I
- Current: what the appliance draws in amps (A), which sets the fuse and cable size
Watts to amps
| Power | 230 V (A) | 120 V (A) | 400 V three-phase (A) | 12 V DC (A) | 24 V DC (A) |
|---|---|---|---|---|---|
| 5 W | 0.02174 | 0.04167 | 0.007217 | 0.4167 | 0.2083 |
| 10 W | 0.04348 | 0.08333 | 0.01443 | 0.8333 | 0.4167 |
| 20 W | 0.08696 | 0.1667 | 0.02887 | 1.667 | 0.8333 |
| 50 W | 0.2174 | 0.4167 | 0.07217 | 4.167 | 2.083 |
| 60 W | 0.2609 | 0.5 | 0.0866 | 5 | 2.5 |
| 100 W | 0.4348 | 0.8333 | 0.1443 | 8.333 | 4.167 |
| 150 W | 0.6522 | 1.25 | 0.2165 | 12.5 | 6.25 |
| 200 W | 0.8696 | 1.667 | 0.2887 | 16.67 | 8.333 |
| 300 W | 1.304 | 2.5 | 0.433 | 25 | 12.5 |
| 400 W | 1.739 | 3.333 | 0.5774 | 33.33 | 16.67 |
| 500 W | 2.174 | 4.167 | 0.7217 | 41.67 | 20.83 |
| 600 W | 2.609 | 5 | 0.866 | 50 | 25 |
| 750 W | 3.261 | 6.25 | 1.083 | 62.5 | 31.25 |
| 800 W | 3.478 | 6.667 | 1.155 | 66.67 | 33.33 |
| 1,000 W | 4.348 | 8.333 | 1.443 | 83.33 | 41.67 |
| 1,200 W | 5.217 | 10 | 1.732 | 100 | 50 |
| 1,500 W | 6.522 | 12.5 | 2.165 | 125 | 62.5 |
| 2,000 W | 8.696 | 16.67 | 2.887 | 166.7 | 83.33 |
| 2,200 W | 9.565 | 18.33 | 3.175 | 183.3 | 91.67 |
| 2,500 W | 10.87 | 20.83 | 3.608 | 208.3 | 104.2 |
| 3,000 W | 13.04 | 25 | 4.33 | 250 | 125 |
| 3,500 W | 15.22 | 29.17 | 5.052 | 291.7 | 145.8 |
| 4,000 W | 17.39 | 33.33 | 5.774 | 333.3 | 166.7 |
| 5,000 W | 21.74 | 41.67 | 7.217 | 416.7 | 208.3 |
| 6,000 W | 26.09 | 50 | 8.66 | 500 | 250 |
| 7,000 W | 30.43 | 58.33 | 10.1 | 583.3 | 291.7 |
| 7,500 W | 32.61 | 62.5 | 10.83 | 625 | 312.5 |
| 8,000 W | 34.78 | 66.67 | 11.55 | 666.7 | 333.3 |
| 9,000 W | 39.13 | 75 | 12.99 | 750 | 375 |
| 9,500 W | 41.3 | 79.17 | 13.71 | 791.7 | 395.8 |
| 10,000 W | 43.48 | 83.33 | 14.43 | 833.3 | 416.7 |
| 11,000 W | 47.83 | 91.67 | 15.88 | 916.7 | 458.3 |
A 13 A plug fuse takes up to about 3,000 W at 230 V. On 12 V the same power needs about 19 times the current, which is why low-voltage cables are so thick.
Amps to watts
| Current | 230 V (W) | 120 V (W) | 400 V three-phase (W) | 12 V DC (W) | 24 V DC (W) |
|---|---|---|---|---|---|
| 1 A | 230 | 120 | 692.8 | 12 | 24 |
| 2 A | 460 | 240 | 1386 | 24 | 48 |
| 3 A | 690 | 360 | 2078 | 36 | 72 |
| 5 A | 1150 | 600 | 3464 | 60 | 120 |
| 6 A | 1380 | 720 | 4157 | 72 | 144 |
| 10 A | 2300 | 1200 | 6928 | 120 | 240 |
| 13 A | 2990 | 1560 | 9007 | 156 | 312 |
| 15 A | 3450 | 1800 | 10390 | 180 | 360 |
| 16 A | 3680 | 1920 | 11090 | 192 | 384 |
| 20 A | 4600 | 2400 | 13860 | 240 | 480 |
| 25 A | 5750 | 3000 | 17320 | 300 | 600 |
| 30 A | 6900 | 3600 | 20780 | 360 | 720 |
| 32 A | 7360 | 3840 | 22170 | 384 | 768 |
| 40 A | 9200 | 4800 | 27710 | 480 | 960 |
| 45 A | 10350 | 5400 | 31180 | 540 | 1080 |
| 50 A | 11500 | 6000 | 34640 | 600 | 1200 |
| 63 A | 14490 | 7560 | 43650 | 756 | 1512 |
| 80 A | 18400 | 9600 | 55430 | 960 | 1920 |
| 100 A | 23000 | 12000 | 69280 | 1200 | 2400 |
The most power each fuse or breaker size can carry for simple loads. Leave some headroom: a circuit shouldn't run at its limit for hours, and motors draw several times their running current as they start.
About this chart
How many amps an appliance draws for its power in watts, on UK and European mains (230 V), US mains (120 V), three-phase (400 V) and 12 V or 24 V batteries. Choose Amps to watts above the chart to see how much power each fuse or breaker size can carry.
The figures are for heaters, kettles, lights and other simple loads (a power factor of 1). Motors, pumps and compressors draw more than this; for those, or any other voltage, use the watts to amps calculator.
How it's worked out (power factor 1):
- Single-phase and DC: I = P ÷ V, and P = V × I
- Three-phase: I = P ÷ (√3 × V), and P = √3 × V × I, with V the 400 V between two phases (√3 ≈ 1.732)
- For motors and other loads with a power factor below 1, divide the current by the power factor (a 0.8 power factor draws 25% more amps)
Values are to 4 significant figures, like the calculator. For fixed wiring, cable sizes and breakers, ask a qualified electrician.
Last checked 31 October 2026 · Last rev. 31 October 2026 · 0688