Amps to Watts Calculator
Quickly determine exactly how many watts your device uses by entering its amp reading and the incoming voltage. Essential for measuring small appliance efficiency.
Consumption Calculator
Amps → Watts
Measurement of active power being used by the load.
The Conversion Formula
Power calculation depends on your circuit type — power factor is required for all AC systems.
DC Systems
W = I × V The fundamental power equation — amps times volts equals watts in all DC circuits.
1-Phase AC
W = I × V × PF Power factor accounts for the phase difference between voltage and current, reducing effective real power.
3-Phase AC
W = √3 × I × V × PF Three-phase balanced power sums across all three phases with the √3 (1.732) coefficient for line voltage.
How to Convert Amps to Watts
Converting amperes to watts tells you how much real power a device consumes. This is essential for calculating energy costs, sizing generators, verifying circuit capacity, and comparing appliances. Multiply amps by volts — then apply the power factor for AC systems.
Real Power vs. Apparent Power
Real power (watts) is energy that actually does work — turning a motor, heating an element. Apparent power (VA) is what the supply delivers including reactive current. For heaters and lamps they're equal. For motors and transformers, watts are always lower than VA because some current builds magnetic fields without doing useful work.
Practical Applications
- Energy Cost Calculation: Convert amps to watts, multiply by hours of use to get Wh, divide by 1000 for kWh, then multiply by your electricity tariff.
- Generator Sizing: Sum the watts of all simultaneous loads and add 25% for motor startup surges.
- Circuit Load Audit: Sum all load watts on a circuit. The total should not exceed 80% of the breaker rating × voltage (NEC continuous load rule).
Step-by-Step Conversion
- Read the Current: Measure with a clamp meter or find the amp rating on the device nameplate.
- Note the Voltage: Check your supply — 120V or 240V in North America; 230V in most of Europe.
- Apply Power Factor: Use 1.0 for pure resistive loads. Use 0.8–0.9 for motors and inductive equipment.
- Multiply: I × V for DC; I × V × PF for single-phase AC; √3 × I × V × PF for three-phase AC.