electrical tool
Watts to Amps Calculator
Convert electrical power to current for DC, single-phase, or three-phase systems.
For three-phase AC, voltage is treated as line-to-line voltage. DC uses PF = 1; AC power factor is limited to 0.01–1.
Calculated current
13.9 A
I = P ÷ (V × PF).
Watts to amps guide
How to convert watts to amps
Amps measure current. The current needed by a load depends on its power, voltage, system type, and, for AC equipment, power factor. Choose the matching system type in the calculator and use equipment nameplate values when available.
Formulas
DC
Amps = Watts ÷ Volts
DC does not use AC power factor.
Single-phase AC
Amps = Watts ÷ (Volts × PF)
PF is power factor, from 0.01 to 1 in the calculator.
Three-phase AC
Amps = Watts ÷ (√3 × Volts × PF)
The voltage input is line-to-line voltage.
Worked examples
DC: 1,200 W ÷ 120 V = 10 A.
Single-phase AC: 1,200 W ÷ (120 V × 0.8 PF) = 12.5 A.
Three-phase AC: 6,000 W ÷ (√3 × 240 V × 0.9 PF) ≈ 16.0 A.
Watts-to-amps reference table
These examples assume PF = 1. The 240 V three-phase column uses 240 V line-to-line voltage.
| Watts | 120 V DC | 120 V single-phase | 240 V single-phase | 240 V three-phase |
|---|---|---|---|---|
| 100 W | 0.83 A | 0.83 A | 0.42 A | 0.24 A |
| 500 W | 4.17 A | 4.17 A | 2.08 A | 1.20 A |
| 1,000 W | 8.33 A | 8.33 A | 4.17 A | 2.41 A |
| 1,500 W | 12.50 A | 12.50 A | 6.25 A | 3.61 A |
| 3,000 W | 25.00 A | 25.00 A | 12.50 A | 7.22 A |
When power factor matters
Power factor matters for AC loads because not all current contributes directly to real power. Use the manufacturer's value for motors, compressors, pumps, air conditioners, and other inductive or electronic loads. If no value is available, treat the result as an estimate rather than assuming the equipment will match the table.
Common applications
This conversion is useful when checking appliance nameplates, estimating circuit current for a known load, comparing generator or inverter loads, and translating solar or battery system power into approximate current. It does not determine safe wiring, breaker, or home-connection requirements.
Frequently asked questions
How do I convert watts to amps?
Divide watts by volts for DC. For single-phase AC, divide watts by volts multiplied by power factor. For three-phase AC, divide watts by the square root of 3, volts, and power factor.
What power factor should I use?
Use the power factor from the equipment documentation when available. Resistive loads are often close to 1, while motors, compressors, and other inductive loads can have lower power factors.
Does the three-phase calculation use line-to-line voltage?
Yes. This calculator treats the three-phase AC voltage input as line-to-line voltage.
Is the result a guaranteed equipment rating?
No. The result is a planning calculation. Confirm nameplate information, system voltage, power factor, and installation requirements with the equipment documentation and a qualified professional.
Electricity cost guide
Estimate electricity cost from kWh and your rate
This calculator first estimates energy use from power and time, then applies your electricity rate. Enter your own rate instead of treating a default as universal.
Formula
cost = kWh × electricity rate
The page estimates kWh from watts × hours per day × days ÷ 1,000 before multiplying by the rate.
Worked examples
Daily: 1,000 W used for 2 hours is 2 kWh. At $0.18/kWh, the estimate is $0.36 per day.
30-day period: 2 kWh daily for 30 days is 60 kWh. At $0.18/kWh, the energy-only estimate is $10.80.
Example rate table
| Selected-period energy | Entered rate | Estimated energy cost |
|---|---|---|
| 60 kWh | $0.15/kWh | $9.00 |
| 60 kWh | $0.18/kWh | $10.80 |
| 60 kWh | $0.25/kWh | $15.00 |
Limitations
This is an energy-only estimate. Actual utility bills may include taxes, fixed service fees, tiered rates, demand charges, delivery charges, minimums, and other plan-specific items.
Frequently asked questions
How is electricity cost calculated?
Multiply energy used in kWh by the electricity rate in dollars per kWh.
What rate should I enter?
Enter the rate shown on your utility bill or plan. Rates vary by provider, location, time, and billing structure.
Why might my actual bill be different?
Bills can include taxes, fixed fees, tiers, demand charges, delivery charges, minimums, and other utility-specific adjustments that are outside this simple estimate.
Can I estimate a monthly cost?
Yes. Enter average watts, hours per day, and the number of days in your period, then enter the applicable rate.
Important assumptions
This is a planning estimate, not a guarantee of performance. Real equipment varies with temperature, age, power quality, duty cycle, wiring, and manufacturer specifications.