kW to Amps Calculator
Convert between power, current and kVA for DC, single-phase and three-phase circuits — with power factor. Free, no sign-up.
Circuit Details
Formulas Used
- Three-phase: I = P × 1000 / (√3 × V × cos φ)
- Single-phase: I = P × 1000 / (V × cos φ)
- DC: I = P × 1000 / V
- kVA = kW / cos φ · kVAr = √(kVA² − kW²)
This converter gives the steady-state design current for a stated power and power factor. Motor starting currents, harmonics, diversity and cable sizing to BS 7671 are separate questions — for a compliant design, see our ProDesign cable calculation service.
How to Convert kW to Amps
For a three-phase AC load: I = P × 1000 / (√3 × V × cos φ). A 30 kW motor on a 400 V three-phase supply at 0.85 power factor draws 30,000 / (1.732 × 400 × 0.85) ≈ 51 A. The same 30 kW on a single-phase 230 V supply would draw about 153 A — which is why larger loads are three-phase.
Why Power Factor Matters
Cables and protective devices see current, not useful power. At 0.8 power factor a load draws 25% more current than the same kW at unity — so an optimistic power factor assumption undersizes everything downstream. If you don't know the power factor, 0.95 is a reasonable assumption for modern equipment with power factor correction; motors without correction are typically 0.8–0.85 at full load.
kW, kVA and kVAr
Real power (kW) does the work; apparent power (kVA) is what the network must carry; reactive power (kVAr) is the difference that circulates without doing work: kVA = kW / cos φ, and kVAr = √(kVA² − kW²). Transformers and generators are rated in kVA — another reason the power factor of your load schedule matters.