What is the kVA to amps formula?

For single-phase, I = kVA × 1000 ÷ V. For three-phase, I = kVA × 1000 ÷ (√3 × V), where √3 ≈ 1.732 and V is the line-to-line voltage.

Does power factor matter for kVA to amps?

No. kVA is apparent power, which already combines real and reactive power, so the current depends only on kVA and voltage. Power factor matters when converting kW to amps, not kVA to amps.

Why is there a √3 for three-phase?

In a balanced three-phase system the total apparent power is √3 × line-to-line voltage × line current. Rearranging for current introduces the √3, which is why the same kVA gives a lower current at the same voltage in three-phase than single-phase.

Which voltage do I use for three-phase?

Always the line-to-line (phase-to-phase) voltage — 208, 240, 480, or 600 V. Do not use the line-to-neutral value; the √3 formula already accounts for the phase relationship.

How do I size a breaker from this?

The result is the full-load current. For continuous loads apply NEC 125% and round up to the next standard overcurrent device, and check conductor ampacity separately. The nameplate current is the starting point, not the final breaker size.

kVA to Amps Converter

Reading a transformer nameplate in amps

Transformers, generators, and UPS units are rated in kVA — apparent power — but electricians need amps to size conductors, breakers, and disconnects. The conversion depends only on the kVA and the voltage, never on power factor, because kVA already bundles the real and reactive components together. This converter handles single-phase and three-phase systems at all the common North American voltages and shows the exact formula it used so you can check the work.

How it works

For a single-phase (or split-phase line-to-line) system the line current is:

I = kVA × 1000 / V

For a balanced three-phase system the apparent power is √3 × V × I, so solving for current gives:

I = kVA × 1000 / (√3 × V)

with V always the line-to-line voltage and √3 ≈ 1.732. Because three-phase spreads the same apparent power across three conductors, the same kVA at the same voltage produces a noticeably lower per-line current than single-phase would.

Example and notes

A 75 kVA three-phase transformer at 480 V has a full-load current of 75 × 1000 ÷ (1.732 × 480) ≈ 90.2 A. The same 75 kVA single-phase at 240 V would draw 312.5 A — over three times the current — which is exactly why distribution is done three-phase at higher voltage. Use the result as the starting full-load current: for continuous loads multiply by 1.25 before selecting the overcurrent device, round up to the next standard breaker size, and verify the conductor ampacity (including any temperature or bundling derating) separately.