# Single Phase Power Calculator

> Calculate single phase power step by step: P = V × I × PF; S = V × I.

Page: https://freecalculator.tech/tools/single-phase-power-calculator
Last reviewed: 2026-11-03

## Formula

P = V × I × PF; S = V × I.

- Use RMS voltage and current.
- Power factor between 0 and 1; use 1 for a purely resistive load.
- Result is real power in watts.
- P = V × I × PF; S = V × I.
- Inputs used: Voltage (RMS), Current (RMS), Power factor.

## Inputs

- Voltage (RMS)
- Current (RMS)
- Power factor

## Worked example: 230 V, 10 A, PF 0.9

Single-phase motor.
1. S = 230 × 10 = 2,300 VA.
2. P = 2,300 × 0.9 = 2,070 W.

## Common questions

### What power factor should I enter?

Use the nameplate or a measured value. Resistive heaters are close to 1; motors are often lower, especially lightly loaded.

### Why is watts less than VA?

With PF below 1, part of the current does no useful work, so real power is smaller than apparent power.

### Is this for 120 V as well?

Yes — enter any single-phase voltage.

### How do I use the Single Phase Power Calculator?

Enter the required values for Voltage (RMS), Current (RMS), Power factor. The calculator applies the formula on this page and shows the main result with any supporting breakdown so you can check the arithmetic.

### What formula does the Single Phase Power Calculator use?

P = V × I × PF; S = V × I. The visible formula section above lists the calculation path and the edge cases the page handles, so the result can be checked without relying on the form alone.

### Can the Single Phase Power Calculator be used for exact decisions?

Use it as a calculation aid, not as a substitute for checking the underlying rule, contract, policy, or professional advice that applies to your situation. When a result depends on local rules, personal details, prices, or dates, enter those values yourself and confirm them before acting.

## Limitations and assumptions

- Sinusoidal supply assumed.
- Uses a single steady power factor.
- Efficiency of the driven machine is not included.
- Results are estimates for planning and learning. Real designs, installations and bids must be checked by a qualified, licensed professional against the codes that apply where you work.
- The result depends on the values you enter for this single phase power calculator; it does not supply missing rates, rules, prices, dates, or assumptions for you.

## Sources

- OpenStax (Rice University) — https://openstax.org/details/books/university-physics-volume-2

## Cite this page

- APA: Free Calculator. (2026, November 3). Single Phase Power Calculator. https://freecalculator.tech/tools/single-phase-power-calculator
- MLA: "Single Phase Power Calculator." Free Calculator, 3 Nov. 2026, https://freecalculator.tech/tools/single-phase-power-calculator.
- Link: Single Phase Power Calculator — Free Calculator, https://freecalculator.tech/tools/single-phase-power-calculator