Amps to kVA Calculator
Turn a measured or nameplate current into apparent power. Enter the amps and the voltage — single-phase or three-phase — and get the kVA the load actually represents.
Balanced three-phase load, line-to-line voltage. Change any value and the result updates instantly.
The amps to kVA formulas
This is the kVA to amps conversion run backwards: instead of dividing apparent power by the voltage, you multiply the current by it. The √3 belongs to three-phase for the same geometric reason it appears in the forward direction.
One live conductor: multiply the current by the voltage to get volt-amps, then divide by 1000 for kVA.
The standard three-phase form, using the line-to-line voltage printed on nameplates (400V, 480V).
When the voltage you have is line-to-neutral — 230V in a 400V system, for example — use 3 × instead of √3 ×.
Worked examples
A 40 A home EV charger on a 240V supply: 40 × 240 ÷ 1000 is a 9.60 kVA load. That is the number to compare against a home generator or UPS rating — not the 40 A alone.
A 200 A residential service at 240V single-phase carries 200 × 240 ÷ 1000 = 48.00 kVA at most. A backup generator advertised as "whole house" for that panel needs a rating in that neighbourhood before any load management.
A three-phase circuit protected at 63 A on a 400V supply: √3 × 63 × 400 ÷ 1000 = 43.65 kVA. Useful when a machine's plate gives current but the supply or transformer is specified in kVA.
Amps to kVA reference table
Common breaker and circuit sizes turned into kVA at the three most asked-about voltages. Anything in between is one multiplication away in the calculator above.
| Current | 240V · single-phase (kVA) | 400V · three-phase (kVA) | 480V · three-phase (kVA) |
|---|---|---|---|
| 10 A | 2.40 | 6.93 | 8.31 |
| 16 A | 3.84 | 11.09 | 13.30 |
| 20 A | 4.80 | 13.86 | 16.63 |
| 32 A | 7.68 | 22.17 | 26.60 |
| 40 A | 9.60 | 27.71 | 33.26 |
| 50 A | 12.00 | 34.64 | 41.57 |
| 63 A | 15.12 | 43.65 | 52.38 |
| 80 A | 19.20 | 55.43 | 66.51 |
| 100 A | 24.00 | 69.28 | 83.14 |
| 125 A | 30.00 | 86.60 | 103.92 |
| 160 A | 38.40 | 110.85 | 133.02 |
| 200 A | 48.00 | 138.56 | 166.28 |
When to be careful
A clamp reading is a moment, not a rating
Current measured on a running load rises and falls with the work the load is doing. Converting a single reading gives the kVA at that moment. For sizing, use the nameplate current or the protective device's rating — the largest current the circuit is designed to carry — rather than one quiet-afternoon measurement.
Starting current is not in this conversion
Motors and compressors draw several times their running current for a moment at start. That surge matters for generator and UPS sizing, but it is not part of the amps-to-kVA identity, and no steady-state conversion can show it. Check the equipment's starting or locked-rotor figures separately.
Frequently asked questions
How many kVA is 100 amps?
At 240 V single-phase, 100 A is 24.00 kVA. At 400 V three-phase it is 69.28 kVA, and at 480 V three-phase it is 83.14 kVA. The same current means very different power on different supplies, so the voltage and phase always come first.
How do I convert amps to kVA three-phase?
Multiply the current by the line-to-line voltage and by √3, then divide by 1000: kVA = √3 × A × V ÷ 1000. Example: 63 A at 400 V is 1.732 × 63 × 400 ÷ 1000 = 43.65 kVA. If your voltage is line-to-neutral, use 3 × A × V ÷ 1000 instead.
Is amps to kVA just the reverse of kVA to amps?
Yes — both directions come from the same identity. Apparent power equals volts × amps single-phase, or √3 × volts × amps three-phase. Converting to amps divides by the voltage; converting back to kVA multiplies by it. Nothing else enters either direction.
What size generator do I need for a 100 amp load?
First turn the load into kVA at your voltage: 100 A at 240 V single-phase is 24.00 kVA, so the generator must be rated at least that — and in practice you pick the next standard size up, a 25 or 30 kVA set, so the machine is not running at its limit continuously. At 400 V three-phase the same 100 A is 69.28 kVA, a very different machine. The generator calculator lists standard sizes with their full-load amps.
Does power factor matter when converting amps to kVA?
No. Amps and kVA are linked by voltage alone (and √3 three-phase). Power factor only appears when kW enters the question — converting kVA to kW, or amps to kW. If a tool asks for a power factor to give you kVA from amps, it is mixing two different conversions.
Sources and references
The identities used here are the same standards-based formulas as the main converter, run in reverse. See the methodology page for the derivations.
- NFPA 70 — National Electrical Code (NEC) — the code electricians size conductors and protection against
- IEEE Std 141 — Recommended Practice for Electric Power Distribution (Red Book) — apparent power and load-current practice for industrial and commercial systems
- IEC 60038 — Standard Voltages — the standard voltage levels (120, 208, 240, 400, 480 V) used across this site
- NIST — SI unit of electric current (the ampere) — the definition of the ampere behind every result