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kW to Amps Calculator

For single-phase or DC power, amps = kW × 1,000 ÷ (volts × power factor). For three-phase, divide by √3 (1.732) as well. The default 10 kW at 240 V with a power factor of 1 draws 41.7 A. As a continuous load it needs a 52.1 A circuit, so a 60 A breaker is the next standard size.

By Izhar Ahmad DanishUpdated Sources cited

kW
V

Single phase: A = kW × 1,000 ÷ (V × PF). Three phase: A = kW × 1,000 ÷ (√3 × V × PF). Continuous loads: size the circuit at 125% of running amps.

Current

41.7 A

Minimum circuit for a continuous load (125%)52.1 A
Next standard breaker size60 A
Apparent power10 kVA

Key numbers

  • Single phase: A = kW × 1,000 ÷ (V × PF)
  • Three phase: A = kW × 1,000 ÷ (√3 × V × PF)
  • 10 kW at 240 V = 41.7 A; 125% for continuous use = 52.1 A → 60 A breaker
  • 1 kW = 8.3 A at 120 V, 4.2 A at 240 V, 1.2 A at 480 V three-phase
On this page
  1. How to use the kW to Amps
  2. How to convert kW to amps
  3. kW to amps conversion table (PF = 1)
  4. From amps to breaker size
  5. kVA to amps
  6. What affects the result
  7. History of the watt and the ampere
  8. References
  9. Frequently asked questions

How to use the kW to Amps

  1. 1Enter your numbersFill in power (kW), voltage (V), circuit and power factor. Every field starts with a typical value you can overwrite.
  2. 2Check the assumptionsSingle phase: A = kW × 1,000 ÷ (V × PF). Three phase: A = kW × 1,000 ÷ (√3 × V × PF). Continuous loads: size the circuit at 125% of running amps.
  3. 3Read the resultsThe calculator shows current, minimum circuit for a continuous load (125%), next standard breaker size and apparent power, and updates as you type.
  4. 4Use the resultCompare it with your bill, a quote or a product spec sheet before you buy or install anything.

Results update as you type. Back to the calculator ↑

This kW to amps calculator converts power in kilowatts into the current a circuit has to carry, for single-phase, three-phase and DC loads. Enter the kW rating, the voltage, the circuit type and the power factor. You get the running amps, the minimum circuit size for a continuous load, the next standard breaker size and the apparent power in kVA. To go the other way, use the amps to kW calculator.

How to convert kW to amps

Kilowatts alone do not tell you the current. You also need the voltage and, for AC motors and electronics, the power factor (PF), the ratio of real to apparent power defined in IEEE Std 1459-2010:

  • DC: A = kW × 1,000 ÷ V
  • Single-phase AC: A = kW × 1,000 ÷ (V × PF)
  • Three-phase AC: A = kW × 1,000 ÷ (√3 × V × PF), where V is line-to-line voltage and √3 ≈ 1.732

Worked example with the default values

  1. Power 10 kW, voltage 240 V, single phase, PF 1
  2. Current: 10 × 1,000 ÷ (240 × 1) = 41.7 A
  3. Continuous-load circuit: 41.7 × 1.25 = 52.1 A
  4. Next standard breaker: 60 A

On a 480 V three-phase supply with a motor at PF 0.85, the same 10 kW draws 10,000 ÷ (1.732 × 480 × 0.85) = 14.1 A per phase.

kW to amps conversion table (PF = 1)

kW 120 V single 240 V single 208 V three-phase 480 V three-phase
1 kW 8.3 A 4.2 A 2.8 A 1.2 A
5 kW 41.7 A 20.8 A 13.9 A 6.0 A
7.2 kW 60.0 A 30.0 A 20.0 A 8.7 A
10 kW 83.3 A 41.7 A 27.8 A 12.0 A
11.5 kW 95.8 A 47.9 A 31.9 A 13.8 A
20 kW 166.7 A 83.3 A 55.5 A 24.1 A
50 kW 416.7 A 208.3 A 138.8 A 60.1 A
100 kW 833.3 A 416.7 A 277.6 A 120.3 A

For a power factor below 1, divide the table value by the PF. A 5 kW motor at 240 V and PF 0.8 draws 20.8 ÷ 0.8 = 26 A.

From amps to breaker size

In the US, the National Electrical Code sizes circuits for continuous loads, those running three hours or more, at 125% of the running current. That is the same as keeping the load at or below 80% of the breaker. Round the result up to the next standard breaker rating (15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100 A and so on).

Load at 240 V kW Running amps × 1.25 Breaker
Electric water heater 4.5 kW 18.8 A 23.4 A 25 A
Level 2 EV charger (32 A) 7.2 kW 30.0 A 37.5 A 40 A
Level 2 EV charger (48 A) 11.5 kW 47.9 A 59.9 A 60 A
Electric furnace 15 kW 62.5 A 78.1 A 80 A

Air conditioners, heat pumps and other motor equipment are different. Their nameplates list a minimum circuit ampacity (MCA) and a maximum overcurrent protection (MOP), and those numbers, not this calculation, set the wire and breaker size.

kVA to amps

Transformers, generators and UPS units are often rated in kVA, which already includes the power factor. Use amps = kVA × 1,000 ÷ V for single-phase and ÷ (1.732 × V) for three-phase. A 15 kVA transformer at 208 V three-phase supplies up to 15,000 ÷ (1.732 × 208) = 41.6 A.

What affects the result

  • Voltage. US homes have 120 V and 240 V circuits; many commercial buildings use 208 V or 480 V three-phase. Higher voltage means fewer amps for the same power, which is why EV chargers and dryers use 240 V.
  • Power factor. Heaters and ovens are close to 1. Motors and compressors are lower, and the DOE notes that motor power factor falls further at light load.
  • Line vs phase voltage. The three-phase formula uses line-to-line voltage. With phase-to-neutral voltage, divide by 3 × V × PF instead.
  • Starting current. Motors draw several times their running current for a moment at start-up.

Watch out

This calculator gives estimates. Have a licensed electrician size breakers and wiring, especially for EV chargers, heat pumps, solar inverters and other renewable energy equipment.

To see what a load costs to run, enter its kW in the electricity cost calculator. For charger sizing and charging costs, try the EV charging cost calculator, and convert units with the kW to watts converter. Our guide what is a kilowatt-hour explains how kW of power turn into kWh on your bill.

History of the watt and the ampere

The watt is named after James Watt, the Scottish engineer whose improved steam engine helped drive the Industrial Revolution. Carl Wilhelm Siemens proposed the name for the unit of power in 1882, and the British Association for the Advancement of Science adopted it the same year (Watt). The ampere had become a unit of current in 1881. The watt became an SI unit when the International System of Units was set up in 1960, and in the 2019 SI revision the ampere was redefined by fixing the value of the elementary charge (NIST SP 330). Because a watt is a volt times an ampere, the kW to amps formula in this calculator follows straight from those definitions.

Year Milestone
1881 Ampere adopted as the unit of current
1882 British Association adopts the watt, proposed by C. W. Siemens
1960 Watt and ampere become SI units
2019 Ampere redefined through the elementary charge

References

  • IEEE Std 1459-2010. “IEEE Standard Definitions for the Measurement of Electric Power Quantities Under Sinusoidal, Nonsinusoidal, Balanced, or Unbalanced Conditions.” doi:10.1109/IEEESTD.2010.5439063
  • Newell, D. B. & Tiesinga, E. (eds.) (2019). The International System of Units (SI). NIST Special Publication 330. doi:10.6028/NIST.SP.330-2019
  • U.S. Department of Energy. Determining Electric Motor Load and Efficiency (fact sheet). energy.gov

FAQ

Frequently asked questions

How do I convert kW to amps?

Multiply kilowatts by 1,000 to get watts, then divide by the voltage and the power factor. A 3 kW heater on 240 volts draws 3,000 ÷ 240 = 12.5 amps. For three-phase power, also divide by 1.732 and use the line-to-line voltage.

How many amps is 10 kW?

At a power factor of 1, 10 kW draws 83.3 amps at 120 volts, 41.7 amps at 240 volts, 27.8 amps at 208 volts three-phase and 12.0 amps at 480 volts three-phase. You always need the voltage to convert kilowatts to amps.

How many amps is 1 kW?

1 kW draws about 8.3 amps at 120 volts, 4.2 amps at 240 volts, 2.8 amps at 208 volts three-phase and 1.2 amps at 480 volts three-phase, assuming a power factor of 1. Motors with a lower power factor draw more.

How do I convert kW to amps for three-phase power?

Divide watts by √3 × line-to-line voltage × power factor. A 20 kW motor load at 480 volts and a power factor of 0.85 draws 20,000 ÷ (1.732 × 480 × 0.85) = 28.3 amps per phase.

What size breaker do I need for my kW load?

Convert kW to amps, multiply by 1.25 for a continuous load, then round up to the next standard breaker size. An 11.5 kW EV charger on 240 volts draws 47.9 amps; 47.9 × 1.25 = 59.9 amps, so it needs a 60 amp breaker. Have an electrician confirm wire size and local code.

What is the difference between kW and kVA when converting to amps?

kW is real power and kVA is apparent power. Amps follow from kVA directly: amps = kVA × 1,000 ÷ volts (÷ 1.732 for three-phase), with no power factor. If you only know kW, divide by the power factor to get kVA first.

5 Sources

  1. NFPA 70, National Electrical Code (continuous load and breaker sizing provisions)
  2. U.S. DOE, Determining electric motor load and efficiency
  3. IEEE Std 1459-2010, Definitions for the measurement of electric power quantities
  4. NIST, SP 330: The International System of Units (2019)
  5. Wikipedia, Watt (history of the unit)

Last updated October 25, 2026. Part of our renewable energy toolkit. Found an error? Tell us.