Amps to kVA conversion turns a measured current into apparent power. It answers the question every generator buyer faces: if my equipment draws 100 amps, how large a generator do I need? The conversion depends on current, voltage, and phase configuration — it does not require power factor.
Apparent power for a balanced three-phase system using line-to-line voltage. The √3 factor (1.732) accounts for the three-conductor delivery.
Apparent power for a single-phase system. The √3 factor disappears because power is delivered across two conductors only.
Power factor converts apparent power to real power. At 0.8 PF, 69.3 kVA equals 55.4 kW. PF does not affect the amps-to-kVA conversion itself.
The square root of three appears because a three-phase supply delivers power continuously across three conductors that are 120 degrees out of phase. For the same current, a three-phase system delivers 1.732× more kVA than a single-phase system. That is why industrial equipment and generator sets are overwhelmingly three-phase — more power per ampere of conductor.
kVA is apparent power. The kVA that corresponds to a given current is fixed by voltage and phase — power factor only enters when you convert to kW.
The three-phase formula uses line-to-line voltage. If working from line-to-neutral, use kVA = (3 × VLN × A) ÷ 1000.
If phases carry unequal currents, size from the highest phase. Estimate as kVA = (√3 × V × highest-phase-amps) ÷ 1000.
To convert kVA to amps: Amps = (kVA × 1000) ÷ (√3 × Volts). Use this when you already have a generator and need its full-load current.
Convert measured line current into apparent power (kVA) and real power (kW) for single-phase and three-phase systems. Use the result to size a generator, check an existing load, or compare across voltage systems.
Results are estimates for planning. Confirm final sizing with an engineer.
For quick reference, the table below lists three-phase apparent power for common line currents at 400 V (IEC/global standard) and 480 V (North American industrial). These values assume balanced loads at standard voltages.
| Line Current (Amps) | kVA @ 400 V | kVA @ 480 V |
|---|---|---|
| 10 A | 6.9 kVA | 8.3 kVA |
| 25 A | 17.3 kVA | 20.8 kVA |
| 50 A | 34.6 kVA | 41.6 kVA |
| 100 A | 69.3 kVA | 83.1 kVA |
| 150 A | 103.9 kVA | 124.7 kVA |
| 250 A | 173.2 kVA | 207.8 kVA |
| 500 A | 346.4 kVA | 415.7 kVA |
| 1000 A | 692.8 kVA | 831.4 kVA |
| 2000 A | 1385.6 kVA | 1662.8 kVA |
Example 1: A 100 A load at 400 V, three-phase — 69.3 kVA.
Example 2: A 150 A load at 440 V, three-phase — 114.3 kVA.
Example 3: The same 100 A at 240 V single-phase — 24 kVA. For the same current, three-phase delivers 1.732× more apparent power.
The kVA figure from the calculator above is the starting point for selecting the right generator. Follow these five steps to turn your measured current into a practical generator recommendation.
Get the amps number from a nameplate full-load amps (FLA), a clamp-meter reading of the running load, or the sum of branch-circuit currents on your panel schedule. For motor-driven equipment, account for starting surge separately.
Enter the current and your supply voltage into the calculator above. For a three-phase system, the result is the apparent power your generator must supply. For single-phase, the formula removes the √3 factor.
Multiply by power factor to see real power. At 0.8 PF, a 69.3 kVA load equals 55.4 kW. Generator sets are commonly rated in kVA at 0.8 power factor, so both numbers matter when comparing machines.
Do not run a generator at 100% of rated load. Aim for 70–80% loading for continuous duty, and add headroom for motor starting surge. A common rule is to size 20–25% above your steady-state kVA.
Round up to the next standard generator rating — 80 kVA, 100 kVA, and so on. Browse our diesel generator sets from 8 kVA to 4000 kVA and confirm the correct machine with an engineer.
At Shandong Huali Electromechanical Co., Ltd., we manufacture diesel generator sets from 8 kVA to 4000 kVA, engineered for continuous industrial operation with over 25 years of experience and strict pre-delivery testing on every unit.
A: Multiply line-to-line voltage by current and by √3, then divide by 1000: kVA = (√3 × Volts × Amps) ÷ 1000. For example, 100 A at 400 V is 69.3 kVA.
A: At 400 V three-phase, 100 A equals about 69.3 kVA. At 480 V the same current delivers about 83.1 kVA. Higher voltage means more apparent power for the same current.
A: No. kVA is apparent power, which already includes the full load current. Power factor only enters when you convert to kilowatts using kW = (√3 × Volts × Amps × PF) ÷ 1000.
A: For the same current, a three-phase system delivers 1.732× more kVA than a single-phase system. Three-phase power distributes the load across three conductors, which is why industrial equipment is three-phase.
A: Measure your load current, convert it to kVA with the calculator above, then multiply by power factor for kW. Add 20–25% margin for motor starting surge, and round up to the next standard generator rating.
