kW to Volts Calculator

About the kW to Volts Calculator

A kW to volts calculator determines the circuit voltage from known real power (kW) and current (amps), using the relationship V = (kW × 1000) / (A × PF). This reverse calculation is used in circuit diagnosis, cable voltage drop analysis, and electrical system auditing — situations where power consumption and current are measurable but the supply voltage needs to be verified or calculated. In practice, this calculation is most useful when commissioning or troubleshooting electrical systems: if you know a motor is rated at 3.7 kW and is drawing 17.8 amps, you can calculate the expected line voltage and compare against your measurement to detect voltage problems. Our calculator supports both single-phase and three-phase configurations and includes the power factor adjustment needed for realistic AC circuit calculations, making it applicable for residential, commercial, and industrial electrical work across all voltage systems globally.

How It Works

V = (kW × 1000) / (A × PF). For three-phase calculations with line-to-line voltage: V_LL = (kW × 1000) / (A × PF × √3). Example 1 (diagnosis): a single-phase motor is rated at 2.2 kW and measures 19.2A. Expected PF ≈ 0.95. V = (2,200) / (19.2 × 0.95) = 2,200 / 18.24 = 120.6V — confirming nominal 120V supply. Example 2 (cable drop analysis): a 5 kW resistive load at the end of a long run draws 22A. Measured voltage at load = V = 5,000 / 22 = 227.3V instead of expected 240V. Voltage drop = 12.7V = 5.3% — potentially exceeding the 3% recommendation for branch circuits. Example 3 (3-phase): 15 kW pump draws 28A at PF 0.88. V_LL = 15,000 / (28 × 0.88 × 1.732) = 15,000 / 42.7 = 351V — below nominal 380V, indicating a voltage problem.

Tips & Best Practices

• ✓Voltage drop diagnosis: NEC recommends maximum 3% voltage drop on branch circuits and 5% total (feeder + branch). If calculated voltage is significantly below nominal, check conductor sizing, connection quality, and transformer tap settings.
• ✓Power factor measurement: use a true-power-factor meter or power analyzer for accurate PF measurement on inductive or capacitive loads. Standard clamp ammeters measure RMS current but do not account for PF — using assumed PF = 1 in the formula gives apparent power only.

Who Uses This Calculator

Electricians and technicians diagnosing voltage problems by comparing measured current against expected voltage from rated power. Engineers performing cable voltage drop analysis for long circuit runs. System commissioning engineers verifying supply voltage against equipment specifications. Students learning to apply Ohm's Law and AC power formulas to real-world electrical problems.