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Free calculator

Use this calculator to

  • Convert a circuit's voltage and current straight into watts
  • Check the maximum wattage of a socket, fused spur or site transformer outlet
  • Work out what 12 V and 110 V low-voltage equipment draws in watts
  • Sense-check appliance nameplates that quote amps but not watts

Volts to Watts Calculator

Convert voltage (V) to power (W).

V
A
Result
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Formulas

  • W = V × A

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Common scenarios

Select one to run it in the calculator above.

For business

Why this matters for businesses

Working out the real power draw of a piece of equipment from its supply voltage and current is one of the most useful tasks an energy auditor performs on site. A 230V single-phase load drawing 8A at a power factor of 0.85 pulls 1,564W, not the 1,840W an apparent-power reading would suggest. That 276W gap, multiplied across a few hundred loads on a multi-site portfolio, is the difference between an honest baseload profile and a misleading one. The watts figure is what shows up on the supplier bill, so it is the one to trust.

For SMEs and mid-market operators, the practical use is identifying baseload candidates: the kit that sits on overnight and at weekends, drawing real power for no commercial output. Server cabinets, CCTV systems, vending machines and refrigeration cabinets are the usual suspects. Convert their measured voltage and current into watts, multiply by 8,760 hours, and the result is annual kWh consumption. From there it is a straight commercial decision whether to replace, switch off or schedule the equipment.

Purely Energy delivers this kind of analysis as part of a wider procurement strategy across the 2,000+ sites we manage. We help businesses turn meter and sub-meter data into a ranked list of efficiency opportunities, prioritised by payback. That feeds into the supply contract decision (volume forecast, shape, off-peak vs peak split) so the procurement saving compounds with the consumption saving. The result is typically a 15 to 30% reduction in total energy spend over the contract term.

Common questions

How do I convert volts to watts?

Multiply voltage by current: W = V x A. A 230 V circuit carrying 5 A delivers 1,150 W. Voltage alone cannot give you watts, so this calculator also needs the current; read it from the appliance nameplate, the breaker rating or a clamp meter measurement.

How many watts can a 13 A socket supply?

230 V x 13 A = 2,990 W, so just under 3 kW. That is why the most powerful plug-in appliances (kettles, fan heaters, washer-dryers) are rated at 3 kW or below. Anything larger must be hardwired to a dedicated circuit with a higher current rating.

Does W = V x A hold for AC circuits?

For resistive loads (heaters, kettles, incandescent lamps), yes. For motors, drives and electronics, the real power is W = V x A x PF, where the power factor accounts for current that flows without delivering work. The plain V x A product on an AC circuit is the apparent power in VA, not watts.

What does 110 V site equipment draw in watts?

UK construction sites use 110 V centre-tapped transformers for portable tools. A 16 A outlet at 110 V supplies up to 110 x 16 = 1,760 W, which is why site tools are typically rated below 1.8 kW. The centre tap limits each leg to 55 V to earth, reducing the shock risk.

Are watts and volt-amps the same thing?

Only at unity power factor. Watts measure real power, volt-amps measure apparent power, and W = VA x PF. For a heater they coincide; for a motor at 0.85 power factor, 1,000 VA of supply capacity delivers just 850 W of real power. Cables and breakers are sized on VA, while energy metering counts watts over time.

Related calculators

The conversions that procurement and engineering use alongside this one.

Volts to Watts Calculator | Purely Energy