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Wattage Calculator

Calculate electrical power (watts) from voltage and current, with optional power factor.

Introduction

Wattage Calculator — Calculate electrical power (watts) from voltage and current, with optional power factor. Enter Voltage (V), Current (A), Power factor to get an instant, accurate result.

Formula

Power = Voltage × Current (P = V × I). If a power factor is entered, P = V × I × PF, since power factor reduces real power delivered relative to what voltage and current alone would suggest.

Step-by-step

  1. Enter the Voltage (V).
  2. Enter the Current (A).
  3. Enter the Power factor.
  4. Click Calculate to see your result instantly.

Real-world example

Example: With Voltage (V) = 120, Current (A) = 10, Power factor = 1, the Wattage Calculator gives Watts: 1200, Power Factor Used: 1.

Frequently Asked Questions

What is power factor and when do I need it?
Power factor (0 to 1) accounts for the phase difference between voltage and current in AC circuits with motors or other reactive loads. For simple resistive loads (heaters, incandescent bulbs) it is effectively 1 and can be left blank.
Does this work for both AC and DC circuits?
Yes — for DC or purely resistive AC loads, power factor is 1 and P = V × I applies directly.
What inputs does the Wattage Calculator need?
You'll need to provide: Voltage (V), Current (A), Power factor. All fields use sensible defaults, so you can see a working example immediately and then adjust the values to match your own numbers.
How accurate is the Wattage Calculator?
The Wattage Calculator applies the formula exactly as calculated — Power = Voltage × Current (P = V × I). If a power factor is entered, P = V × I × PF, since power factor reduces real power delivered relative to what voltage and current alone would suggest. — so results are precise for the inputs you provide. Accuracy depends on entering correct, realistic input values.
Is the Wattage Calculator free to use?
Yes, the Wattage Calculator is completely free, requires no signup, and runs instantly in your browser.

About the Wattage Calculator

The Wattage Calculator uses a real, verifiable formula — Power = Voltage × Current (P = V × I). If a power factor is entered, P = V × I × PF, since power factor reduces real power delivered relative to what voltage and current alone would suggest. — so results are accurate every time, not an approximation.