kVA (kilovolt-amperes) is apparent power — the total power a supply delivers, including any reactive component. Amps is the current flowing to deliver it. Converting between them only needs the supply voltage and whether the circuit is single-phase or three-phase — no lookup tables involved.
For a single-phase supply: kVA = (A × V) ÷ 1000, so A = (kVA × 1000) ÷ V. For a three-phase supply: kVA = (A × V × √3) ÷ 1000, so A = (kVA × 1000) ÷ (V × √3). Both directions use the same relationship rearranged — this converter runs whichever form matches the direction you've selected above.
√3 (approximately 1.732) accounts for the 120° phase offset between the three supply legs. Because the three phases don't peak at the same instant, the total power delivered isn't simply three times a single phase's contribution — it works out to line-to-line voltage multiplied by current and by √3. This factor only applies to three-phase calculations; single-phase conversions are a straightforward V × A.
kVA is apparent power: everything the supply has to provide, including current that does no useful work (reactive power, drawn by motors, transformers, and similar inductive loads). kW is real power — the portion actually converted into useful output. The two are related by the power factor, typically 0.8–0.95 for most electrical equipment: kW = kVA × power factor. This converter assumes unity power factor (1.0) and works in apparent power only — it does not convert to kW.
The voltage field accepts any value — the conversion itself is standard V × A arithmetic and works identically whatever figure you enter. The preset buttons are shortcuts for the values used most often in UK electrical work: 230V for single-phase, 400V for three-phase line-to-line, 110V for site/construction transformers, and 415V for the older nominal three-phase figure some equipment nameplates still quote. Use whichever preset matches your actual supply, or type the exact voltage if you know it.