Amps to kW Calculator - DC, Single-Phase and Three-Phase

Agarapu Ramesh — Editor and content reviewer
Editorially reviewed Reviewed by Agarapu Ramesh, science educator (chemistry). LinkedIn
Last reviewed: May 2026 | Standard electrical engineering formulas

Amps are current. kW is real power. To get from one to the other you need voltage, and for AC you need power factor. For three-phase work, use line voltage and the sqrt(3) factor.

Formula at a glance

  • DC: kW = V x A / 1000
  • single-phase: kW = V x A x PF / 1000
  • three-phase: kW = 1.732 x V x A x PF / 1000

Field note: Do not use breaker size as the running current unless you have nothing else. A 32 A breaker does not mean the load draws 32 A all day.

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Calculator Tool

Convert amperes to kilowatts

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V
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Formulas

DCkW = (I×V) ÷ 1000
AC 1-PhasekW = (I×V×PF) ÷ 1000
AC 3-PhasekW = (√3×I×V×PF) ÷ 1000

Quick Reference @240V

Amps kW (DC)
10A 2.4 kW
20A 4.8 kW
30A 7.2 kW
50A 12 kW

Related Calculators

kW to Amps Amps to Watts

How to use the Amps to kW Calculator

Use this as a fast electrical check, then compare the result with the nameplate, measured voltage and power factor. The formula is clean. Real panels, motors and UPS loads usually have one extra wrinkle.

Worked example

Example: 20 A at 230 V single-phase with PF 0.9 gives 4.14 kW. On a 415 V three-phase circuit at the same current and PF, it gives 12.94 kW.

Practical checks before you trust the number

  • Power factor matters on motors, welders, pumps, LED drivers and UPS loads.
  • For heaters, kettles and incandescent lamps, PF is close to 1.
  • Measure voltage under load when you can. Site voltage is not always the tidy number printed on the panel.

Common mistake

Do not use breaker size as the running current unless you have nothing else. A 32 A breaker does not mean the load draws 32 A all day.

Sources and references

Related calculators

Frequently Asked Questions

kW = (V × A × PF) ÷ 1000 for single-phase, or kW = (√3 × V × A × PF) ÷ 1000 for three-phase. DC: kW = (V × A) ÷ 1000. Example: 230 V × 20 A × 0.9 PF ÷ 1000 = 4.14 kW. This converts measured current into a real power figure for billing, sizing, or load auditing — one of the most-used calculations in any energy walk-through.

DC: kW = (V × A) ÷ 1000. Example: 48 V battery bank delivering 100 A → kW = (48 × 100) ÷ 1000 = 4.8 kW. No PF, no √3. This is the formula we use for solar and EV calculations daily. Just remember to use the actual operating voltage, not the nominal one — a 48 V system might run at 52 to 56 V in float mode.

kW = (V × A × PF) ÷ 1000. Example: 230 V × 12 A × 0.9 ÷ 1000 = 2.48 kW. For resistive loads PF = 1, so 230 × 12 ÷ 1000 = 2.76 kW. Always include PF for inductive loads, otherwise your real-power figure is overstated. This is the formula behind every kWh meter reading on a single-phase residential connection.

Three-phase: kW = (√3 × V_line × A × PF) ÷ 1000 = (1.732 × V × A × PF) ÷ 1000. Example: 415 V, 20 A, PF 0.85 → kW = (1.732 × 415 × 20 × 0.85) ÷ 1000 = 12.2 kW. Always use line-to-line voltage. Forgetting the √3 is the most common three-phase mistake — it gives a number 1.732 times too small and underestimates the real load.

Lower PF means less of the current actually does work. kW = V × A × PF, so at the same V and A, low PF gives low kW. Example: 415 V × 25 A on three-phase = 17.97 kVA apparent. At PF 0.85 → kW = 17.97 × 0.85 = 15.3 kW. The 2.7 kW difference is reactive power that flows uselessly. Improve PF with capacitor banks and you cut billable kW and cable losses.

Single-phase, PF 1: kW = (240 × 30) ÷ 1000 = 7.2 kW. Single-phase, PF 0.85: kW = (240 × 30 × 0.85) ÷ 1000 = 6.12 kW. So a 30 A circuit at 240 V handles roughly 6 to 7 kW depending on load type. For heaters, you get the upper figure; for compressors, the lower. We size feeders for the worst-case PF to avoid trips.

Yes, exactly. Sum the amps from your panel measurements, multiply by V and PF, and you get the connected real-power load in kW. Example: a residential panel pulling 35 A at 230 V, PF 0.9 → 7.25 kW. Compare this with the meter and breaker rating to spot overloads or unbalanced phases. Run this check during commissioning and again at the first quarterly maintenance visit.