kW Calculator (AC/DC • 1-Phase / 3-Phase)

How to Use the kW Calculator

AC (Single Phase)

Select AC, choose 1-Phase, enter the line-to-neutral voltage, current (A), and power factor (PF). The tool instantly shows W, kW, and MW.

AC (Three Phase)

Select AC, choose 3-Phase, enter the line-to-line voltage, current (A), and PF. The three-phase formula includes √3 to account for phase relationships.

DC

Select DC, enter voltage (V) and current (A). Power factor is not used in DC, so the calculator forces PF = 1.00.

Formulas Used

AC 1-Phase: kW = (V × I × PF) / 1000

AC 3-Phase: kW = (√3 × V × I × PF) / 1000

DC: kW = (V × I) / 1000

Conversions: W = kW × 1000, MW = kW / 1000

Example Calculation

For a 3-phase load at 400 V (L-L), 20 A, PF 0.90: kW ≈ √3 × 400 × 20 × 0.90 / 1000 ≈ 12.47 kW.

FAQ

What’s the difference between kW and kVA?

kW is real power (does work). kVA is apparent power (based on voltage and current). PF links them.

Why does 3-phase use √3?

In balanced 3-phase systems, total power uses √3 × (line voltage) × (line current) × PF.

Which voltage should I enter for 3-phase?

Enter line-to-line (L-L) voltage for 3-phase calculations (e.g., 400 V, 415 V, 480 V).

Which voltage should I enter for single-phase?

Enter line-to-neutral (L-N) voltage (e.g., 230 V in many regions).

What power factor should I use if I don’t know it?

For motors, 0.85–0.95 is common. For heaters/resistive loads, use 1.00.

Why is PF disabled in DC mode?

Power factor describes AC phase angle effects. DC has no phase angle, so PF is 1 by definition.

Can I use this for quick generator or UPS sizing?

You can use it for quick real-power estimates, but sizing also needs kVA, starting currents, and design margins.

Are the results final for construction drawings?

No—use this for preliminary checks. Always verify with detailed design calculations and project standards.

About This Tool

This kW calculator is built for MEP engineers and draftsmen to quickly estimate electrical real power from voltage and current. It supports AC single/three-phase and DC systems with instant auto-calculation.