kVA Calculator — Apparent Power, Real Power & Power Factor
Calculate apparent power (kVA), real power (kW) and reactive power (kVAR) for any AC electrical circuit. Enter voltage and current, or switch mode to input real power or apparent power directly, along with the power factor.
Known quantities
V
A
kVA = kW ÷ power factor — the total load the supply must deliver
- 1
Volt-amperes (VA)
230 × 10 = 2 300 - 2
Apparent power kVA = VA ÷ 1000
2 300 ÷ 1000 = 2,300
Comment fonctionne cette calculatrice ?
kVA = V × I / 1000 (apparent power). kW = kVA × PF (real power). kVAR = kVA × √(1 − PF²) (reactive power). Power factor PF = kW / kVA ranges 0–1; at PF 1 all kVA equals kW. Low PF means the supply must source more kVA than the load actually uses productively.
Formule
How this is calculated
In an alternating current (AC) system, three distinct power quantities describe how energy flows. Real power (P, kW) is the power actually converted to useful work — heat, light, motion. Apparent power (S, kVA) is the total power supplied by the generator or transformer, the product of RMS voltage and RMS current. Reactive power (Q, kVAR) is the power that oscillates between the source and inductive/capacitive loads (motors, transformers) without performing net work.
The three form a right triangle — the power triangle — where S² = P² + Q². The power factor (PF = cos φ) is the ratio P/S, ranging from 0 (purely reactive) to 1.0 (purely resistive, perfect efficiency). A low power factor means the supply must deliver more kVA to provide the same kW of useful work, increasing cable sizes, transformer ratings, and energy costs. Utilities often penalise industrial customers with PF below 0.85–0.95.
This calculator works for balanced single-phase or three-phase equivalent circuits. For three-phase systems, multiply the single-phase kVA by 3 (for three single-phase loads) or use √3 × V_line × I_line / 1000 as the apparent power — the per-phase power factor relationship remains the same.
Questions fréquentes
kW (kilowatts) is real power — the useful work done. kVA (kilovolt-amperes) is apparent power — the total load the electrical supply must handle. kVA = kW ÷ power factor. When the power factor is 1.0, kVA = kW. For a motor with PF 0.8, a 10 kW load draws 12.5 kVA from the supply.
The power factor is usually on the equipment nameplate or in the technical datasheet. Resistive loads (heaters, incandescent bulbs) have PF ≈ 1.0; induction motors typically run at 0.7–0.9; fluorescent lighting without correction is often 0.5–0.6. A clamp meter that measures both watts and VA can calculate PF directly.
Generators and UPS systems are rated in kVA, not kW, because they must supply apparent power. Size your generator by summing the kVA of all loads (using each load's PF) and adding a 20–25% safety margin. A 10 kW load at PF 0.8 requires at least 12.5 kVA, so a 15 kVA generator is typical for that load.
Aussi appelé
TG we-Calculate Editorial Team. (2026). kVA Calculator — Apparent Power, Real Power & Power Factor [Online calculator]. TG we-Calculate. https://we-calculate.com/fr/calculator/kva-calculator
TG we-Calculate Editorial Team. "kVA Calculator — Apparent Power, Real Power & Power Factor." TG we-Calculate. 2026. https://we-calculate.com/fr/calculator/kva-calculator.
TG we-Calculate Editorial Team, "kVA Calculator — Apparent Power, Real Power & Power Factor," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/fr/calculator/kva-calculator
@misc{wecalculate_kva_calculator, title = {kVA Calculator — Apparent Power, Real Power & Power Factor}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/fr/calculator/kva-calculator}}, year = {2026}, note = {TG we-Calculate} }
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