Calculateur watts vers VA
Convertit la puissance active (W) en puissance apparente (VA): VA = W ÷ FP. Pratique pour UPS, onduleurs et dimensionnement.
Watts from nameplate or measured device load.
Between 0 and 1. Lower PF means higher VA for the same watts.
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Table of Contents
Why convert watts to VA
Watts (W) is real power. VA is apparent power used to rate UPS systems, transformers, and inverters.
In AC systems with PF below 1, apparent power is higher than real power for the same load.
That is why equipment may list two limits, like 1500VA / 900W.
Use this conversion when your load is in watts but your equipment capacity is specified in VA.
Formula
Watts to VA
VA = W ÷ PF
PF is between 0 and 1 for most loads.
Related forms
W = VA × PF | PF = W ÷ VA
If PF = 1 (purely resistive assumption), watts and VA are equal.
How this links to other electrical formulas
For real AC power from volts and amps: W = V × I × PF (single-phase) and W = √3 × VL-L × I × PF (balanced three-phase, line-to-line).
Quick Reference Table
| Watts | PF | VA | Typical load |
|---|---|---|---|
| 100 W | 1.0 | 100 VA | Resistive heater estimate |
| 120 W | 0.8 | 150 VA | Small adapter / mixed load |
| 900 W | 0.9 | 1000 VA | UPS planning example |
| 1700 W | 0.85 | 2000 VA | Motor-heavy load |
FAQ
For normal AC definitions, no. With PF ≤ 1, converting watts to apparent power gives VA ≥ W.
Use device specs when available. For rough planning, many electronic loads are around 0.8–0.95.
VA is mainly used for AC ratings. For DC, power is usually handled directly in watts.
This tool starts from real power (W) and estimates required apparent power. VA-to-watts does the inverse.