kVA, kW and Amps Converter
Type a figure in kVA, kW, amps or horsepower and see all the others for single phase, three phase or DC. Advanced adds line-to-neutral volts, motor efficiency and a table of amps for common sizes.
0.8 is the common rating basis for generators. Homes: 230 V in India, the UK, Europe and the Gulf, 120 V in the US. For three phase, type the voltage between two lines (for example 400 V or 480 V).
Line to line is the usual figure (400 V, 415 V, 480 V). Line to neutral is the phase voltage (230 V, 240 V, 277 V): then kVA = 3 × volts × amps.
A motor's rating plate gives its shaft output in hp or kW and its efficiency. The electrical input is the output ÷ efficiency, and that is what the amps are worked out from. Small motors are often 75–85% efficient, large ones 90–96%.
Amps for common kVA sizes
| Size | kW at 0.8 PF | Amps |
|---|
Full-load current of a generator or transformer of each size. Pick cables and breakers for the current with an electrician.
How your conversion is worked out
Turn your figure into volt-amps or watts, use the power factor to go between kVA and kW, divide by the voltage for amps, then convert to horsepower.
- 1
Your figure
10 kVA × 1,000= 10,000 VA
- 2
kVA and kW
10 kVA × 0.8 PF= 8 kW6 kVAR reactive
- 3
Amps
10,000 VA ÷ 230 V= 43.48 A
- 4
Horsepower
8,000 W ÷ 745.7= 10.73 hp27,297 BTU/h
Read more: the formulas, a worked example, a table of amps and notes on power factor
kVA, kW and amps are three views of the same load. kVA (apparent power) is volts × amps, the figure cables, transformers and generators are sized by. kW (real power) is the part that does useful work: kVA × power factor. Amps follow from kVA and the voltage, with an extra √3 on three phase. Horsepower and BTU/h are just kW in other units.
The formula
kW = kVA × power factor
kVA = kW ÷ power factor
kVAR = √(kVA² − kW²)
single phase and DC: amps = VA ÷ volts = watts ÷ (volts × power factor)
three phase (line to line): amps = VA ÷ (1.732 × volts)
three phase (line to neutral): amps = VA ÷ (3 × volts)
kVA from amps = volts × amps (× 1.732 on three phase) ÷ 1,000
horsepower = watts ÷ 745.7 (metric hp: ÷ 735.5)
motor input watts = shaft hp × 745.7 ÷ efficiency
BTU per hour = watts × 3.412
DC: power factor = 1, so kVA = kW
Worked example
A 10 kVA load on a 230 V single phase supply at a power factor of 0.8:
- In volt-amps: 10 × 1,000 = 10,000 VA.
- Real power: 10 kVA × 0.8 = 8 kW (8,000 W).
- Reactive power: √(10² − 8²) = √(100 − 64) = √36 = 6 kVAR.
- Current: 10,000 VA ÷ 230 V = 43.48 A.
- Horsepower: 8,000 ÷ 745.7 = 10.73 hp, or 8,000 ÷ 735.5 = 10.88 metric hp.
- Heat: 8,000 × 3.41214 = 27,297 BTU/h.
- Phase angle: the angle whose cosine is 0.8, which is 36.87°.
On a three phase 400 V supply the same 10 kVA draws 10,000 ÷ (1.732 × 400) = 10,000 ÷ 692.8 = 14.43 A in each phase. A 10 hp motor (shaft output) that is 90% efficient with a power factor of 0.85 on 400 V three phase takes 10 × 745.7 = 7,457 W ÷ 0.9 = 8,285.6 W in, which is 8,285.6 ÷ 0.85 = 9,747.7 VA, so 9,747.7 ÷ 692.8 = 14.07 A.
Single phase, three phase and DC
On single phase and DC the current flows out on one wire and back on another, so amps = VA ÷ volts. On three phase the power is shared by three wires, so each one carries less: amps = VA ÷ (√3 × line-to-line volts), where √3 ≈ 1.732. If you only know the phase (line-to-neutral) voltage, use 3 × that voltage instead. DC has no power factor, so kW and kVA are the same.
Typical power factors
| Load | Typical power factor |
|---|---|
| Heaters, kettles, filament bulbs | 1.0 |
| Generator ratings (kVA to kW) | 0.8 |
| Induction motors at full load | 0.8 – 0.9 |
| Lightly loaded motors | 0.3 – 0.6 |
| Equipment with power factor correction (good PC power supplies, many LED drivers) | 0.9 – 0.99 |
These are rough typical figures. The rating plate or data sheet of your equipment gives the real one.
Unit conversions used
- 1 kVA = 1,000 VA; 1 MVA = 1,000 kVA. 1 kW = 1,000 W; 1 MW = 1,000 kW.
- 1 mechanical (imperial) horsepower = 745.7 W. 1 metric horsepower (PS, CV, pk) = 735.49875 W.
- 1 W = 3.412 BTU per hour, so 1 ton of cooling (12,000 BTU/h) = 3.517 kW.
Related calculators
Work out volts, amps, ohms and watts on a DC circuit with the Ohm's law calculator. Size a backup set from your appliances with the generator size calculator, and check that a cable carries the current without losing too many volts with the voltage drop calculator.
This converter gives the sums only. Choosing cables, breakers and fuses depends on your local wiring rules, so ask a qualified electrician.
Common questions
How do you convert kVA to kW?
Multiply by the power factor: kW = kVA × PF. At a power factor of 0.8, the common rating basis for generators, 10 kVA = 8 kW and 100 kVA = 80 kW. To go back, kVA = kW ÷ PF.
How many amps is 1 kVA?
It depends on the voltage. Single phase: amps = VA ÷ volts, so 1 kVA is 4.35 A at 230 V, 4.17 A at 240 V and 8.33 A at 120 V. Three phase: amps = VA ÷ (1.732 × volts), so 1 kVA is 1.44 A per phase at 400 V and 1.20 A at 480 V.
How do you work out amps from kW?
Single phase: amps = watts ÷ (volts × power factor). Three phase: amps = watts ÷ (1.732 × volts × power factor). 8 kW at 230 V and PF 0.8 is 8,000 ÷ 184 = 43.48 A; on three phase 400 V it is 8,000 ÷ (1.732 × 400 × 0.8) = 14.43 A per phase.
What is the difference between kVA and kW?
kW is real power: what the load turns into heat, light and motion. kVA is apparent power: volts × amps, which is what cables, breakers, transformers and generators have to carry. The difference is reactive power (kVAR), the current motors and electronics push back and forth. kVA² = kW² + kVAR².
How many kW is 1 horsepower?
One mechanical (imperial) horsepower is 745.7 W, or 0.7457 kW. One metric horsepower (PS, CV or pk) is 735.5 W. A motor's horsepower is usually its shaft output, so the electrical input is higher: divide by the efficiency, for example 10 hp at 90% = 7,457 ÷ 0.9 = 8,286 W.
What power factor should I use?
Use the figure on the rating plate if you have it. Generators are commonly rated in kVA at 0.8. Induction motors are often about 0.8 to 0.9 at full load. Heaters, kettles and filament bulbs are about 1. DC has no power factor, so kW = kVA.
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