Watts to Amps Calculator

Watts do not convert to amps

“How many amps is 2000 watts?” is asked constantly and has no answer on its own. A watt is a rate of doing work. An amp is a rate of charge flowing. The thing that connects them is the voltage, and the voltage is not implied by either number.

The relation is P = V × I, so I = P ÷ V. Every calculator that hands back an answer without asking for a voltage has assumed one — usually the one common where its author lives. That assumption is invisible and it is wrong by nearly a factor of two for a large part of the world.

This tool asks. The region selector is there to make supplying the voltage one click rather than a lookup, and the box below it accepts anything if the installation is not at a nominal figure. But the voltage has to come from somewhere, and pretending otherwise is the failure this page exists to avoid.

The same is true in reverse, and for the third quantity. Amps to watts needs a voltage; watts to volts needs a current. Any two of the three determine the third, and no one of them determines anything.

Your country changes the answer

Mains voltage is roughly 230 V across Europe, the UK, India and Australia, and roughly 120 V across North America, with Japan lower still at 100 V. Current is inversely proportional to voltage, so identical work means a very different current.

This is the reason a 3 kW kettle is unremarkable in Britain and impossible on a standard American outlet. At 230 V it draws 13 A, which a UK ring circuit handles. At 120 V it would draw 25 A, and the outlet is rated for 15. American kettles are therefore about half the power, and take about twice as long — the physics is entirely in the voltage.

It is also why North American houses run large appliances on 240 V split-phase. An oven or a dryer or an EV charger needs the current to be manageable, and the only lever available is to double the voltage. India’s domestic supply is 230 V but three-phase is commonly quoted at 415 V rather than the European 400, which is the same system described with a slightly different nominal.

One caveat worth carrying: these are nominal figures. Both standards allow a tolerance band — a UK supply may legally sit between 216 and 253 V — so a real measurement will differ, and the current with it. For sizing, that tolerance usually matters less than the other margins a wiring code applies, but it is the reason a calculation and a clamp meter disagree.

Watts, volt-amps and power factor

On DC there is one kind of power. On AC there are three, and confusing them is the second-commonest error here after forgetting the voltage.

Real power in watts is work actually done. Apparent power in volt-amps is voltage times current, whatever the phase between them. Reactive power in VAR is the part that flows out and back without doing anything. Power factor is the ratio of the first to the second.

Note the direction, because it is the part people reverse: a worse power factor means more current for the same work. The current is divided by the power factor, not multiplied by it. A 0.7 power factor does not mean 30% of the energy is lost — it means 43% more current has to flow to deliver the same watts.

Power factor is not efficiency, and the distinction is practical rather than pedantic. The extra current is not consumed by the load; it goes out and comes back. But the cable, the breaker, the transformer and the generator all have to carry it, and cable losses go as the square of current. That is why a UPS is rated in VA rather than watts, why large industrial consumers are billed a penalty for poor power factor while domestic meters are not, and why generator sizing is a VA question.

One honest complication: the familiar power factor = cos φ holds only when both voltage and current are sinusoidal. Switch-mode supplies and LED drivers draw current in sharp pulses, and their true power factor is worse than their phase angle implies. The figures in the tool are indicative of a class of equipment rather than measurements, and a modern appliance with active correction can be far better than the number shown.

Three phase and the √3

Three-phase supplies carry a factor of √3 = 1.732, and it appears twice — in two different places, for two different reasons, which is why it is easy to apply once and forget the other.

First, between the two voltages. A three-phase supply has a line-to-neutral voltage and a line-to-line voltage, and the second is √3 times the first. A “400 V” European supply is 230.9 V per phase; a “415 V” Indian one is 239.6; a “208 V” American one is 120. Those pairs are the same system named at either end.

Second, in the power relation. For a balanced load, P = √3 × V_LL× I × PF. Apply the single-phase formula to a three-phase load and the current comes out 1.732 times too high — a 10 kW load at 400 V and PF 0.85 draws 17.0 A per line, not 29.4.

Three-phase distribution exists largely because of the current reduction. The same power split across three conductors means √3 less current in each, and since cable losses go as the square of current, the same copper carries roughly three times the power. It is an economy of wiring rather than a property of the load — and it is also why motors above a few kilowatts are almost always three-phase.

Sizing a circuit from this

The number this page gives is the current a load draws at a stated voltage. That is the starting point of a cable calculation and nowhere near the end of one, and it is worth being explicit about the gap.

A wiring design has to account for how the cable is installed — clipped to a surface, buried in insulation, bunched with others — because each derates its capacity, sometimes by half. It has to account for ambient temperature, for the length of the run and the voltage drop along it, for the fault current the protective device must interrupt, and for whether the load starts gently or draws six times its running current for a second. Motor circuits, in particular, are sized on starting behaviour rather than steady-state current.

Then there is diversity. A consumer unit does not need to supply the sum of every circuit’s maximum at once, and every national code has its own method for deciding how much less. Adding up the currents from a page like this one gives a number that is real but not the number a designer uses.

What this is good for: checking whether an appliance is plausible on a circuit, understanding why an import behaves differently, sanity-checking a quotation, working out whether a generator or a UPS is big enough in VA, and seeing what a power factor is costing. For anything that will actually be installed, the calculation belongs to a qualified electrician working to the code that applies where you are — in most countries that is not merely advisable but a legal requirement.

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Sources and methodology

The nominal voltages here come from the two standards that set them — IEC 60038 for the harmonised 230/400 V system and ANSI C84.1 for the North American 120/240 V one — and they are nominal rather than measured: both standards define a tolerance band around the declared figure, which is why a UK socket can read anywhere from 216 to 253 V and still be compliant. The power definitions follow IEEE 1459, which is also the reason this page is careful to say that power factor equals cos φ only under sinusoidal conditions.

• IEC 60038 — IEC standard voltagesInternational Electrotechnical Commission · verified 2026-09-07 · The harmonised 230 V single-phase and 400 V three-phase nominal values used across Europe, and the tolerance bands that make them nominal rather than measured figures
• ANSI C84.1 — Electric Power Systems and Equipment: Voltage Ratings (60 Hz)National Electrical Manufacturers Association · verified 2026-09-07 · The 120 V and 240 V nominal utilisation voltages in North American practice, and the 208 V three-phase figure that follows from a 120 V wye supply
• IEEE Std 1459 — Definitions for the Measurement of Electric Power QuantitiesInstitute of Electrical and Electronics Engineers · verified 2026-09-07 · The formal definitions of active, reactive and apparent power and of power factor — including that the simple cos φ form holds only for sinusoidal conditions, which is why a distorting load has a worse power factor than its phase angle suggests