kVA (kilovolt-amperes) is apparent power — the total power drawn by a load including any reactive component. Amps is the current flowing in the circuit. Converting between them requires knowing the supply voltage and whether the circuit is single-phase or three-phase.
For single-phase: kVA = (A × V) / 1000, so A = (kVA × 1000) / V. For three-phase: kVA = (A × V × √3) / 1000, so A = (kVA × 1000) / (V × √3). The √3 factor (approximately 1.732) accounts for the phase relationship between the three supply legs. Standard UK voltages are 230V single-phase and 400V three-phase line-to-line.
Note that kVA is apparent power, not kilowatts (kW). To convert to real power you need the power factor of the load — typically 0.8–0.95 for most electrical equipment. This converter assumes unity power factor and gives you apparent power only.