Amps to Watts Calculator
Convert amps to watts (A to W) for DC, single-phase and three-phase circuits
Watts = amps × volts. For example, 10 A at 120 V = 1,200 W. For AC loads multiply by the power factor too, and for three-phase multiply by √3 × volts × amps × power factor.
Amps to watts calculator
LiveThree-phase uses line-to-line voltage. For wiring decisions, follow local electrical code.
How to convert amps to watts
An amp is a flow of electric charge of one coulomb per second, and a volt is the energy each coulomb carries, one joule per coulomb. Multiply the two and the coulombs cancel, leaving joules per second, which is the definition of a watt. That is why the conversion is P = V × I, and why you cannot turn amps into watts without knowing the voltage: 10 A is 120 W on a 12 V battery circuit but 1,200 W on a 120 V outlet. When you know the watts and need the current, the watts to amps calculator is the mirror image, and the full set of electrical calculators adds Ohm's law, kVA and voltage drop.
Step by step
- Read the current in amps from the nameplate, the breaker or a clamp meter.
- Confirm the voltage: typically 12 V or 24 V for DC systems, 120 V or 240 V in North America and 230 V in most other countries.
- Multiply volts × amps. For AC loads, also multiply by the power factor; for three-phase, multiply by √3 (about 1.732) as well.
- Divide by 1,000 if you want kilowatts. The calculator shows both.
Worked examples
- Vacuum cleaner, 120 V: a nameplate of 10 A means 120 × 10 = 1,200 W at a power factor of 1. If the motor's power factor is 0.8, the real power is 0.8 × 120 × 10 = 960 W.
- European socket, 230 V: 16 A × 230 V = 3,680 W, or 3.68 kW, the most a Schuko outlet is rated to deliver.
- Three-phase motor: 20 A per line at 400 V with a power factor of 0.85 is 1.732 × 0.85 × 400 × 20 = 11,778 W, about 11.78 kW.
Once you have watts, the kW to hp converter shows the same figure as horsepower, which helps when you compare a motor's electrical input with its nameplate hp.
The power triangle
- P = V × I
- I = P ÷ V
- V = P ÷ I
- Three-phase: P = √3 × V × I × PF
How many watts is a 30 amp RV hookup?
A 30 A RV hookup supplies up to 3,600 W, because it is a single 120 V circuit on a NEMA TT-30 outlet: 30 A × 120 V = 3,600 W.
A 50 A hookup (NEMA 14-50) is a different animal. It brings two 120 V legs of 50 A each, so it can deliver 2 × 50 × 120 = 12,000 W, more than three times as much. For loads that run for hours, such as air conditioning, plan on about 80% of each figure.
| Hookup | Supply | Maximum | At 80% for long-running loads |
|---|---|---|---|
| 15 A household outlet (NEMA 5-15) | 120 V | 1,800 W | 1,440 W |
| 30 A RV hookup (NEMA TT-30) | 120 V | 3,600 W | 2,880 W |
| 50 A RV hookup (NEMA 14-50) | 120/240 V, two 50 A legs | 12,000 W | 9,600 W |
Add up the watts of everything that runs at once, such as the air conditioner, water heater, microwave and chargers, and compare the total with the limit to see whether the pedestal breaker will trip. Use a proper adapter rather than a homemade one, and have a licensed electrician install any RV outlet at home, following your local electrical code.
How many watts can a 200 amp service supply?
A 200 A, 120/240 V residential service can supply up to 200 × 240 = 48,000 W, or 48 kW, at its full rating.
| Service rating | Amps × 240 V | Kilowatts |
|---|---|---|
| 100 A | 24,000 W | 24 kW |
| 150 A | 36,000 W | 36 kW |
| 200 A | 48,000 W | 48 kW |
| 400 A | 96,000 W | 96 kW |
That number is a ceiling, not a design target. How much load a panel may carry comes from a load calculation under NEC Article 220, which applies demand factors because not everything runs at once. The result decides whether a heat pump, an EV charger or an induction range fits on the existing service.
Split-phase service delivers 240 V across its two legs, so a 200 A service means up to 200 A on each leg, not 400 A in total. Have a licensed electrician carry out the load calculation and any service upgrade, following your local electrical code.
Amps to watts chart
Calculated with a power factor of 1 (resistive loads such as heaters and incandescent bulbs). Motors and electronics with a lower power factor draw more current for the same watts.
| Current | 12 V DC | 120 V AC | 230 V AC | 240 V AC |
|---|---|---|---|---|
| 0.5 A | 6 W | 60 W | 115 W | 120 W |
| 1 A | 12 W | 120 W | 230 W | 240 W |
| 2 A | 24 W | 240 W | 460 W | 480 W |
| 5 A | 60 W | 600 W | 1,150 W | 1,200 W |
| 10 A | 120 W | 1,200 W | 2,300 W | 2,400 W |
| 13 A | 156 W | 1,560 W | 2,990 W | 3,120 W |
| 15 A | 180 W | 1,800 W | 3,450 W | 3,600 W |
| 16 A | 192 W | 1,920 W | 3,680 W | 3,840 W |
| 20 A | 240 W | 2,400 W | 4,600 W | 4,800 W |
| 30 A | 360 W | 3,600 W | 6,900 W | 7,200 W |
Watts vs volt-amperes: what is the difference?
Multiplying volts by amps gives volt-amperes, and only part of that may be real power in watts. The difference decides both your energy bill and the size of a generator or UPS.
| Attribute | Watts (W) | Volt-amperes (VA) |
|---|---|---|
| Kind of power | Real (active) power that does work or makes heat | Apparent power: volts × amps, whatever the phase angle |
| Single-phase formula | P = V × I × PF | S = V × I |
| Equal when | The power factor is 1: heaters, kettles, incandescent lamps, DC circuits | Same condition; otherwise VA is the larger number |
| Rated on | Appliance labels; your meter bills it as kWh | UPS units, generators and transformers, often in kVA |
| Example: 10 A at 120 V, power factor 0.8 | 960 W | 1,200 VA |
4 key differences
- Volts × amps always gives volt-amperes, and it equals watts only when the power factor is 1.
- A UPS rated 1,500 VA at a power factor of 0.9 can supply at most 1,350 W, so check both ratings, because either can be the limit.
- IEC 80000-6 reserves the watt for real power and gives apparent power the volt-ampere and reactive power the var.
- Current, not real power, heats cables and trips breakers, so circuits are sized from amps while energy bills follow watts.
How many watts can a circuit breaker supply?
A breaker can supply its amp rating times the circuit voltage, and continuous loads are generally held to 80% of that figure. Maximum power for common North American breaker sizes, from P = V × I, and the 80% figure the US National Electrical Code generally applies to continuous loads (those running three hours or more). Add up everything that can run at once on a circuit and compare it with these limits.
| Circuit | Maximum watts | 80% continuous load | Continuous amps |
|---|---|---|---|
| 15 A at 120 V | 1,800 W | 1,440 W | 12 A |
| 20 A at 120 V | 2,400 W | 1,920 W | 16 A |
| 20 A at 240 V | 4,800 W | 3,840 W | 16 A |
| 30 A at 240 V | 7,200 W | 5,760 W | 24 A |
| 40 A at 240 V | 9,600 W | 7,680 W | 32 A |
| 50 A at 240 V | 12,000 W | 9,600 W | 40 A |
| 60 A at 240 V | 14,400 W | 11,520 W | 48 A |
How many watts can a plug or outlet deliver?
A plug can deliver its rated current times the supply voltage: 1,800 W for a US NEMA 5-15, 2,990 W for a UK 13 A plug and 3,680 W for a European Schuko. The rated current of common household plugs multiplied by the nominal supply voltage. These are ceilings, not targets: the wiring behind the outlet and the breaker protecting it may set a lower limit. Travel adapters change the plug shape, not the voltage, so check the appliance's rating before using it abroad.
| Plug / outlet | Rated current | Nominal voltage | Maximum power |
|---|---|---|---|
| US / Canada NEMA 5-15 | 15 A | 120 V | 1,800 W |
| US / Canada NEMA 5-20 | 20 A | 120 V | 2,400 W |
| UK BS 1363 (fused plug) | 13 A | 230 V | 2,990 W |
| Europe Schuko (CEE 7/4) | 16 A | 230 V | 3,680 W |
| Australia / NZ AS/NZS 3112 | 10 A | 230 V | 2,300 W |
Amp-hours to watt-hours for batteries
Battery capacity in amp-hours becomes energy in watt-hours with the same multiplication: Wh = V × Ah. The last column is the ideal run time for a 100 W load. Real run time is shorter because of inverter losses and because many batteries should not be fully discharged. For energy in other units, see the kWh to BTU converter.
| Battery | Energy | Energy (kWh) | Ideal run time at 100 W |
|---|---|---|---|
| 3.7 V, 5 Ah | 18.5 Wh | 0.018 kWh | 0.2 h |
| 12 V, 7 Ah | 84 Wh | 0.084 kWh | 0.8 h |
| 12 V, 50 Ah | 600 Wh | 0.600 kWh | 6.0 h |
| 12 V, 100 Ah | 1,200 Wh | 1.200 kWh | 12.0 h |
| 24 V, 100 Ah | 2,400 Wh | 2.400 kWh | 24.0 h |
| 48 V, 100 Ah | 4,800 Wh | 4.800 kWh | 48.0 h |
Why is volts × amps not always watts?
Because volts × amps gives apparent power in volt-amperes (VA), which equals real power in watts only when the power factor is 1. For DC and resistive AC loads such as heaters, toasters and incandescent lamps, VA and watts are the same. Loads with motors, compressors or electronic power supplies often have a power factor below 1, so part of the current flows back and forth without doing work, and the real power in watts is lower than V × I.
This matters in two directions. When you estimate energy use or running cost, multiply by the power factor, because your meter bills for real power in kilowatt-hours; the watts to kW converter gets you to the kilowatt figure. When you size a generator, UPS or inverter, look at its VA rating as well as its watt rating, because the current, not the watts, is what heats the wiring and trips the breaker. If you know the resistance of a load instead of its current, the Ohm's law calculator gives power as V² ÷ R.
What do the amps on an appliance nameplate mean?
They are the most current the appliance is designed to draw at its rated voltage, not what it draws every minute it is switched on.
- Rated amps are a maximum. The label shows the highest current the appliance is designed to draw. A refrigerator or air conditioner cycles, so its average power over a day is far below volts × rated amps.
- Starting current is higher. Motors draw a brief inrush at start-up that can be several times the running current. Generators need extra headroom for this surge.
- Dual-voltage labels. A label such as 100–240 V, 1.5 A gives the maximum current at the lowest voltage. At 230 V the same device draws less current for the same power.
- Three-phase labels list the current in each line. Use the three-phase setting and the line-to-line voltage.
Safety note: the calculator is for estimating and learning. Circuit capacity, breaker size and wire gauge are set by your local electrical code, such as the NEC in the US or IEC-based national rules elsewhere. Have a licensed electrician carry out any wiring or panel work.
Sources and further reading
The standards and references behind the numbers on this page. Links open in a new tab.
Standards and official sources
Further reading
- Electric powerWikipedia
Amps to watts FAQs
Short, exact answers to what people ask most.
How many watts is 10 amps?
At 120 V, 10 A is 1,200 W. At 230 V it is 2,300 W, at 240 V it is 2,400 W and at 12 V DC it is 120 W.
How many watts can a 15 amp circuit handle?
A 15 A circuit at 120 V can supply up to 1,800 W. For continuous loads the usual limit is 80%, or 1,440 W.
How many watts is 20 amps at 240 volts?
20 A × 240 V = 4,800 W. At the 80% continuous-load limit, that is 3,840 W.
How do you convert amps to watts for three-phase?
Multiply √3 × power factor × line-to-line voltage × amps. For example, 20 A at 400 V and a power factor of 0.85 is about 11,778 W.
How many watts is a 13 amp plug?
A UK 13 A fused plug at a nominal 230 V can supply 13 × 230 = 2,990 W, about 3 kW.
How do I convert amp-hours to watt-hours?
Multiply amp-hours by the battery voltage. A 12 V, 100 Ah battery stores 12 × 100 = 1,200 Wh, or 1.2 kWh.
How many watts is 5 amps at 120 volts?
5 A × 120 V = 600 W at a power factor of 1.
How many watts is 1 amp?
It depends on the voltage: 1 A is 120 W at 120 V, 230 W at 230 V and 12 W at 12 V DC.
How many kW is 32 amps at 240 volts?
32 A × 240 V = 7,680 W, or 7.68 kW, the output of a common Level 2 EV charger.
How many watts is 2 amps at 12 volts?
2 A × 12 V = 24 W of DC power.
Related conversions
Unit definitions from the BIPM SI Brochure (9th ed.) and power quantities from IEC 80000-6; continuous-load and service load-calculation rules from the US National Electrical Code (NFPA 70); plug and RV connector ratings from the NEMA WD 6, BS 1363, CEE 7 and AS/NZS 3112 standards. Last updated . How we verify our numbers.