What is the basic watt to amp formula?
For DC circuits, amps equal watts divided by volts. AC calculations also use power factor, and balanced three-phase circuits include the square root of three.
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Watt In Ampere
Calculate amps from watts for DC, single-phase AC, and three-phase circuits using voltage and power factor.
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Quick answers
Watt to Amp Calculator: quick answers
Get concise answers to the most common watt to amp calculator questions before reviewing the formulas, examples, and detailed guidance below.
Can I use the calculator for AC and DC?
Yes. Select DC, single-phase AC, or three-phase AC before entering your values.
Where can I find detailed examples and tables?
Open the dedicated Watt to Amp guide for worked examples, formula derivations, conversion tables, full FAQs, and safety guidance.
Watt to amp definition
What is a watt to ampere conversion?
A watt-to-ampere conversion calculates electrical current from real power and operating voltage. The correct relationship depends on whether the circuit is DC, single-phase AC, or balanced three-phase AC.
Watts measure power; amperes measure current
Watts describe how quickly electrical energy is used or delivered. Amperes describe the rate of electric charge flowing through a circuit. Voltage provides the electrical potential connecting these quantities, while AC calculations may also require power factor and phase configuration.
For example, a 1,200-watt DC load operating at 120 volts draws 10 amperes. The same real power on an AC system can require more current when its power factor is below 1.
Calculation method
How to calculate amps from watts
Follow these steps to choose the correct watt-to-amp formula and avoid common unit or phase errors.
- 1
Identify the circuit
Choose DC, single-phase AC, or balanced three-phase AC.
- 2
Confirm real power
Use watts, or multiply kilowatts by 1,000 before calculating.
- 3
Enter voltage
Use operating voltage; for three phase, use line-to-line voltage.
- 4
Add power factor
For AC loads, use the rated or measured power factor from 0 to 1.
- 5
Apply and verify
Calculate current, then check nameplate data, duty, protection, and code requirements.
Use the calculator result as a planning value. Cable size, breaker rating, starting current, efficiency, derating, and local electrical rules require separate checks.
Electrical formulas
Watt to amp formulas for DC and AC
Select the formula that matches the electrical supply. In every formula, I is current, P is real power, V is voltage, and PF is power factor.
DC circuits
I = P ÷ V
Divide watts by DC voltage.
Example: 1,200 W ÷ 120 V = 10 A
Single-phase AC
I = P ÷ (V × PF)
Divide watts by voltage multiplied by power factor.
Example: 1,840 W ÷ (230 V × 0.8) = 10 A
Three-phase AC
I = P ÷ (√3 × V × PF)
Use line voltage and the square root of three for a balanced load.
Example: 5,543 W ÷ (√3 × 400 V × 0.8) ≈ 10 A
Worked calculations
Watt to amp worked examples
These examples show how voltage, power factor, and phase configuration change the calculated current.
Example 1
DC battery load
Power = 600 W, Voltage = 48 V
I = 600 ÷ 48
12.5 A
A 600-watt DC load at 48 volts draws 12.5 amperes.
Example 2
Single-phase appliance
Power = 2,000 W, Voltage = 230 V, PF = 0.9
I = 2,000 ÷ (230 × 0.9)
9.66 A
The lower power factor increases current above the unity-PF value.
Example 3
Three-phase motor load
Power = 15,000 W, Voltage = 400 V, PF = 0.85
I = 15,000 ÷ (√3 × 400 × 0.85)
25.47 A
This assumes a balanced three-phase load and line-to-line voltage.
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