Power conversion equations
Choose one task. The phase factor is 1 for DC and single-phase AC, and √3 for balanced three-phase AC.
I = S × 1000 / (Fphase × V)P = Fphase × V × I × PF / 1000I = P × 1000 / (Fphase × V × PF)where:
- I
- Calculated current[A]
- P
- Active power[kW]
- V
- System voltage[V]
- PF
- Power factor for AC systems
- S
- Apparent power[kVA]
- Fphase
- 1 for DC or single-phase; √3 for three-phase
Use equipment nameplate current when available, especially for nonlinear loads, motor loads, or equipment with high starting current.
How to convert kW, kVA, and amps
Start by choosing kVA to amps, amps to kW, or kW to amps. The calculator then shows only the system and electrical values required for that task.
- Choose one of the three conversion modes.
- Select DC, single-phase AC, or three-phase AC where available.
- Enter the visible power or current value and voltage.
- Enter power factor for active-power AC conversions.
- Review the result and formula basis before equipment selection.
kW to amps calculation example
A 15 kW balanced three-phase load at 400 V and 0.90 power factor draws approximately 24.1 A.
I = 15,000 / (√3 × 400 × 0.90) = 24.1 A
| Input or result | Value |
|---|---|
| Output power | 15 kW |
| Voltage | 400 V three-phase |
| Power factor | 0.90 |
| Apparent power | 16.7 kVA |
| Line current | 24.1 A |
kW vs. kVA
Kilowatts measure active power, while kilovolt-amperes measure apparent power. For an AC load, kW equals kVA multiplied by power factor. Equipment efficiency belongs in motor or generator output calculations, not this direct electrical conversion.
| Quantity | Meaning | Typical use |
|---|---|---|
| kW | Real power | Useful output or electrical energy converted to work and heat |
| kVA | Apparent power | Transformer, generator, and system loading |
| A | Current | Cable, breaker, contactor, and busbar planning |
Single-phase vs. three-phase current conversion
Single-phase current uses voltage directly in the denominator. Balanced three-phase current uses line-to-line voltage and the √3 factor. DC conversion does not use AC power factor.
Use nameplate current for final equipment selection
Calculated current is an estimate for balanced steady-state conditions. Motors, transformers, rectifiers, variable-speed drives, chargers, and nonlinear loads may have starting current, harmonics, duty cycles, or manufacturer ratings that control final selection.
Three Phase Current CalculatorMotor Current CalculatorCircuit Breaker Size Calculator
Assumptions
- Balanced three-phase load
- Three-phase voltage is line-to-line
- Power factor applies to active-power AC conversions
Important Warnings
- Use nameplate data when available.
- Nonlinear loads, harmonics, and starting current are not included.