kVA to amps calculator
Amps = kVA × 1,000 ÷ volts for single phase, and kVA × 1,000 ÷ (√3 × volts) for three phase. A 75 kVA transformer on 208 V three phase delivers about 208 A.
Full-load current on each line. Size breakers and conductors from the nameplate and the code, not from this figure alone.
- Current per line
- 208.18 A
- Breaker at 125% (continuous)
- 300 A
How it is calculated
- Amps = 75 kVA × 1,000 ÷ (208 V × √3) = 208.18
How to calculate kVA to amps
kVA is volts × amps ÷ 1,000, so the current is the kVA × 1,000 divided by the voltage, and by √3 more on three phase. The worked numbers use the calculator's default: 75 kVA on 208 V three phase.
Step 1: three-phase kVA to amps
Amps = kVA × 1,000 ÷ (√3 × line-to-line volts)
I = S × 1,000 ÷ (1.732 × V)
Example 75 kVA × 1,000 ÷ (1.732 × 208 V) = 208.2 A on each line
Step 2: single-phase kVA to amps
Amps = kVA × 1,000 ÷ volts
I = S × 1,000 ÷ V
Example The same 75 kVA on 240 V single phase: 75 × 1,000 ÷ 240 V = 312.5 A
Step 3: kW to amps needs the power factor
Amps = kW × 1,000 ÷ (√3 × volts × power factor) on three phase; without √3 on single phase
kVA = kW ÷ power factor
Example 75 kW at a power factor of 0.8 on 208 V three phase: 75 × 1,000 ÷ (1.732 × 208 × 0.8) = 260.2 A
Step 4: breaker for a continuous load
Breaker ≥ full-load amps × 1.25, rounded up to the next standard size
Example 208.2 A × 1.25 → 300 A breaker
Transformer and generator protection has its own rules; take the final breaker size from the nameplate and the installation instructions.
kVA to amps chart
A 75 kVA load draws 208.2 A on each line at 208 V three phase, 90.2 A at 480 V three phase and 312.5 A at 240 V single phase.
| kVA | Amps, 240 V single phase | Amps, 208 V three phase | Amps, 480 V three phase |
|---|---|---|---|
| 15 | 62.5 | 41.6 | 18 |
| 30 | 125 | 83.3 | 36.1 |
| 45 | 187.5 | 124.9 | 54.1 |
| 75 | 312.5 | 208.2 | 90.2 |
| 112.5 | 468.8 | 312.3 | 135.3 |
| 150 | 625 | 416.4 | 180.4 |
| 225 | 937.5 | 624.5 | 270.6 |
| 300 | 1,250 | 832.7 | 360.8 |
- 240 V single phase
- 208 V three phase
- 480 V three phase
kVA, kW and amps
kVA is apparent power, the volts × amps a transformer or generator must deliver; kW is the real power. That is why converting kW to amps needs a power factor and converting kVA does not.
Transformers and generators are rated in kVA because the current they carry heats them whatever the power factor of the load.