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Transformer kVA Calculator

Enter voltage, current, and phase to size your transformer in kVA.

How to use

  1. Enter your values in the fields above.
  2. Press Calculate to see your result instantly.
  3. Use the Share button to copy a link to your result.

About this calculator

Transformers are rated in kVA (kilovolt-amperes) rather than kilowatts because that rating describes apparent power — voltage times current — independent of the load's power factor, which the transformer itself doesn't control. For a single-phase load, kVA = (V × A) ÷ 1,000; for a balanced three-phase load, kVA = (V × A × √3) ÷ 1,000, the √3 ≈ 1.732 factor accounting for the phase relationship between the three conductors.

Electricians and engineers size a transformer to the next standard rating above the calculated requirement — common distribution sizes per ANSI/IEEE C57 include 15, 25, 37.5, 50, 75, 100, 167 and 250 kVA — rather than an exact custom size, both because that's what's stocked and to leave headroom for load growth and inrush current.

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