Watts to Amps and Amps to Watts

Written byOleh Soloninupdated 5 October 2026

Direction

Power, W

Active power drawn. A motor's rating plate gives shaft power: divide it by the efficiency first.

Supply

Voltage, V

Single phase: 220 or 230 V; three phase: the line-to-line voltage, 380 or 400 V; direct current: 12, 24 or 48 V.

Advanced options

Power factor

1 for heaters and filament lamps; for anything with a motor, take it from the rating plate.

Result

Current, A10
Power, W2,200
Power, kW2.2
Amps per kilowatt1 kW is 4.55 A at 220 V
Breaker of at least10 A (next rating 13 A)
Supplysingle-phase

I = P ÷ U, and ÷ √3 on three phases

Converts watts and kilowatts to amps and back on 220 and 380 V AC and 12 or 24 V DC, shows the amps per kilowatt, and suggests a breaker no smaller than the current from the IEC 60898-1 range.

Appliances are labelled in watts while breakers and cables are chosen in amps. The conversion is a division by voltage — except on a three-phase supply, where a factor of root three comes in and is regularly forgotten. At 220 V a kilowatt draws 4.55 A; on 380 V three-phase, 1.52 A.

The power factor matters for anything with a motor, which draws more current than a plain division of power by voltage suggests. Heaters and filament lamps sit at 1. For a motor, take the figure from the rating plate.

How to use

Choose the direction: watts to amps or amps to watts.
Pick the supply — single phase, three phase or direct current — and the voltage. For anything with a motor, set the power factor from its rating plate in the advanced fields.
Read the current or power, the amps per kilowatt and the breaker rating that suits the current.

The formulas

Single phase: I = P ÷ (U × PF), P = U × I × PF. Three phase: I = P ÷ (√3 × U × PF), with U the line-to-line voltage. PF is the power factor; it equals cos φ only when voltage and current are sinusoidal, so for a switch-mode power supply take the full power factor from its datasheet. Direct current: I = P ÷ U and P = U × I.

A 2,200 W kettle on 220 V draws 10 A. A 5.5 kW motor on 380 V three-phase: the rating plate gives shaft power, so divide by the efficiency first. At 0.90 efficiency and a power factor of 0.85 it draws 5500 ÷ 0.90 ÷ (1.732 × 380 × 0.85) ≈ 10.92 A; skipping the efficiency would give an understated 9.83 A. A 120 W lamp on 12 V DC draws 10 A, on 24 V 5 A.

Current at a power factor of 1; 12 and 24 V are direct current. Worked out with this calculator.
Power	220 V	380 V, three phase	12 V	24 V
100 W	0.45 A	0.15 A	8.33 A	4.17 A
500 W	2.27 A	0.76 A	41.67 A	20.83 A
1 kW	4.55 A	1.52 A	83.33 A	41.67 A
2 kW	9.09 A	3.04 A	166.67 A	83.33 A
3 kW	13.64 A	4.56 A	250 A	125 A
5 kW	22.73 A	7.6 A	416.67 A	208.33 A

Which breaker for a given load

The preferred rated currents for household circuit breakers under IEC 60898-1 (clause 5.3.2, adopted in Russia as GOST IEC 60898-1-2020) are 6, 8, 10, 13, 16, 20, 25, 32, 40, 50, 63, 80, 100 and 125 A. A breaker must not trip at its rated current (8.6.1); its conventional tripping current is 1.45 times the rating, with a conventional time of one hour up to 63 A (8.6.2).

So the calculator offers the nearest rating no smaller than the current and names the next one up. Several appliances on one circuit add up. The breaker protects the wiring, so the cable must be rated for the breaker — check the cross-section with the wire size calculator.

The load at which the current equals the breaker rating, at a power factor of 1: P = U × I on one phase, P = √3 × U × I on three.
Breaker	220 V, single phase	380 V, three phase
6 A	1.32 kW	3.95 kW
8 A	1.76 kW	5.27 kW
10 A	2.2 kW	6.58 kW
13 A	2.86 kW	8.56 kW
16 A	3.52 kW	10.53 kW
20 A	4.4 kW	13.16 kW
25 A	5.5 kW	16.45 kW
32 A	7.04 kW	21.06 kW
40 A	8.8 kW	26.33 kW
50 A	11 kW	32.91 kW
63 A	13.86 kW	41.47 kW

What this calculator shows

Current in amps, or power in watts and kilowatts
How many amps a kilowatt draws at your voltage
Apparent power in volt-amps when the power factor is below one
A breaker rating no smaller than the current from the IEC 60898-1 range, and the next one up

What to keep in mind

Three phase uses the line-to-line voltage and the root-three formula.
The breaker hint is for AC only and is based on the appliance current alone; cable size is a separate check.

Where the numbers come from

Checked against GOST IEC 60898-1-2020 (IEC 60898-1), clauses 5.3.2 (rated currents), 8.6.1 and 8.6.2 · verified September 2026.

FAQs

How many amps in a kilowatt?

4.55 A at 220 V and 4.35 A at 230 V. On a three-phase 380 V supply the same kilowatt draws 1.52 A, at 400 V 1.44 A. On 12 V DC it is 83.3 A. That is at a power factor of 1; motors draw more.

How do I convert amps to watts?

Multiply current by voltage and by the power factor: P = U × I × cos φ. 16 A at 220 V is 3,520 W, or 3.52 kW. On three phases, add the √3 ≈ 1.732 factor.

How do I pick a breaker from a wattage?

Add up the power of everything on the circuit, work out the current and take a rating no smaller than that from the IEC 60898-1 range — 6, 8, 10, 13, 16, 20, 25, 32, 40, 50, 63 A. Then make sure the cable is rated for that breaker: the breaker protects the wiring, not the appliance.

How many kilowatts can a 16 A breaker carry?

16 A corresponds to 3.52 kW at 220 V, or 10.53 kW on 380 V three-phase, at a power factor of 1. The breaker section has the other ratings.

How do I convert watts to amps on 12 V DC?

Divide power by voltage: I = P ÷ U. A 120 W load draws 10 A at 12 V and 5 A at 24 V. Choose "Direct current" in the calculator.

Why is the three-phase formula different?

Because the three phases are 120 degrees apart and add as vectors, not arithmetically. That is where the root-three factor of about 1.73 comes from.

Worked example

A kettle on a socket

Input: 2,200 W at 220 V, single phase

Output: 10 A, a breaker of at least 10 A

Note: A breaker does not trip at its rated current — IEC 60898-1 requires exactly that. If other appliances share the circuit, add their loads and size the breaker to the total current.

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