kW to Amps Calculator
Convert kilowatts (kW) to amperes (A) for DC, AC single-phase, and AC three-phase circuits, with full power-factor support.
Common conversions
| Input | Result |
|---|---|
| 2 kW DC @ 48 V | 41.67 A |
| 1 kW @ 120 V (1Φ, PF 1) | 8.33 A |
| 5 kW @ 240 V (1Φ, PF 1) | 20.83 A |
| 10 kW @ 240 V (1Φ, PF 0.9) | 46.30 A |
| 20 kW @ 400 V (3Φ, PF 0.9) | 32.07 A |
| 30 kW @ 480 V (3Φ, PF 0.9) | 40.09 A |
| 50 kW @ 480 V (3Φ, PF 0.85) | 70.75 A |
| 100 kW @ 480 V (3Φ, PF 0.85) | 141.51 A |
The math behind it
- A = (10 × 1000) / (240 × 0.9)
- A = 10,000 / 216
- A ≈ 46.30 A
Everything you need to know
Converting kilowatts to amperes lets you size breakers, wire gauges, contactors, and transformers. The relationship depends on the current type (DC vs AC), the system voltage, and, for AC, the power factor of the load.
Picking the right formula
- DC circuits have no power factor; current is simply power divided by voltage.
- Single-phase AC (residential 120/240 V) uses the line voltage and the load's PF.
- Three-phase AC with a line-to-line voltage (208 V, 400 V, 480 V) requires the √3 multiplier.
What is a typical power factor?
Resistive loads (heaters, incandescent bulbs) have PF close to 1.0. Induction motors run between 0.7 and 0.9 at full load. LED drivers and switch-mode power supplies vary from 0.5 to 0.99 depending on whether they include active power factor correction. When in doubt, use the value printed on the equipment nameplate.
Wire and breaker sizing
After calculating amps, apply a continuous-load multiplier of 125% (NEC 210.19 / 215.2 for North America) before selecting your breaker and conductor. For motors, refer to NEC Table 430.250 instead of computing the full-load amps yourself.
Real-world example: wiring a three-phase air compressor
A shop needs to install a 15 kW, 480 V three-phase air compressor with a motor PF of 0.87. Using the three-phase line-to-line formula: A = (15 × 1000) / (√3 × 480 × 0.87) = 15,000 / 723.3 ≈ 20.7 A. Applying the NEC's 125% continuous-load factor brings the minimum breaker size to about 25.9 A, which rounds up to a standard 30 A breaker with 10 AWG copper conductors. Skip the PF term and an installer would calculate only about 18 A, undersizing both the breaker and the wire.
Common applications
After computing amps, multiply by 1.25 for continuous loads (NEC 210.19) and pick the next standard breaker. The same current sets your minimum wire gauge from NEC Table 310.16.
Nameplate kW divided by voltage and PF gives input current. For permit work, NEC Table 430.250 takes precedence over computed values.
A 9.6 kW Level 2 charger at 240 V draws 40 A continuous; that needs a 50 A breaker and 6 AWG copper.
Full-load amps from this calculator are the steady-state value. Locked-rotor current is typically 6-8x higher and dictates contactor and conductor short-circuit ratings.
Common mistakes
Sized exactly to FLA, a breaker on a continuous load will nuisance-trip and the conductor will run hot. NEC requires 125% on circuits expected to run 3+ hours.
Motor nameplate kW is shaft output. Electrical input is shaft kW divided by efficiency (typically 0.88-0.96). Skipping this step underestimates current by 5-15%.
Single-family homes are 240 V; multi-family from a 208/120 V wye gives 208 V between hot legs. A 10 kW load draws 41.7 A at 240 V but 48.1 A at 208 V.
kW must be multiplied by 1000 to get watts before dividing by voltage. Plugging kilowatts straight into a watts-based formula produces a current 1000x too low.
Frequently asked questions
How many amps is 1 kW?+
At 120 V single-phase with PF 1.0, 1 kW is 8.33 A. At 240 V single-phase, 1 kW is 4.17 A. For 3-phase at 480 V line-to-line and PF 1.0, 1 kW is about 1.20 A.
Do I need power factor for resistive loads?+
No, purely resistive loads have PF = 1, so the PF term drops out. Use PF only for inductive loads such as motors, transformers, and many fluorescent ballasts.
Why is √3 used in 3-phase formulas?+
Three-phase line currents sum vectorially 120° apart. The √3 factor (about 1.732) accounts for this geometry when the voltage is measured line-to-line rather than line-to-neutral.
How many amps does a 5 kW single-phase load draw at 240 V?+
About 20.8 A at PF 1.0. With a PF of 0.85, typical for a motor load, current rises to about 24.5 A for the same 5 kW of real power.
Is the kW-to-amps formula different for line-to-neutral three-phase voltage?+
Yes, use a multiplier of 3 instead of √3 when your voltage reading is line-to-neutral (phase voltage) rather than line-to-line.
How many amps does a 50 kW generator supply at 480 V three-phase?+
About 70.7 A at a power factor of 0.85, using the three-phase line-to-line formula with √3.
Do I use the nameplate kW or the input kW for a motor?+
Use input kW, not shaft output kW. Divide the motor's rated output by its efficiency (typically 0.88 to 0.96) to get the actual electrical draw.
How many amps is a 10 kW EV charger at 240 V?+
About 41.7 A at PF 1.0, which is why most 10 kW Level 2 chargers are installed on a 50 A breaker with 6 AWG copper wire.
Can I calculate amps from kW without knowing the power factor?+
No, not accurately for AC circuits. Leaving PF at the default of 1.0 will understate the true current for any inductive load, sometimes by 15% or more.
Why do two loads with the same kW draw different amps?+
Because voltage and power factor both affect current. A 10 kW load draws about 41.7 A at 240 V but only 20.8 A at 480 V, and PF shifts the number further either way.