Watts to Amps Calculator: Convert W to A Online
Calculate electric current in amps from power in watts and voltage.
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How to Use the Watts to Amps Calculator: Convert W to A Online
- 1Enter power in watts (W).
- 2Input voltage (e.g. 120V or 240V).
- 3Select circuit phase (DC, AC Single-Phase, AC 3-Phase).
- 4Read the calculated current in amperes.
Formula & How It Works
Watts to Amps Formula
DC: A = W / V. AC Single: A = W / (V * PF). AC Three: A = W / (sqrt(3) * V * PF).
Worked Examples
Hairdryer on 120V
Input: 1800 W at 120 V (PF 1.0)
Explanation: 1800 / (120 * 1.0) = 15.0 amps.
Space Heater
Input: 1500 W at 120 V (PF 1.0)
Explanation: 1500 / 120 = 12.5 amps.
Electric Water Heater
Input: 4500 W at 240 V (PF 1.0)
Explanation: 4500 / 240 = 18.75 amps.
Frequently Asked Questions
How many amps is 1500 watts at 120 volts?▼
1500 watts / 120 volts = 12.5 amps.
Can a 15-amp breaker handle 1800 watts?▼
1800 W at 120V is exactly 15A. Under the 80% continuous load rule (NEC), maximum continuous load is 1440 W (12A).
What is the formula for watts to amps?▼
Amps = Watts / Volts for DC and resistive AC circuits.
What is power factor (PF)?▼
Power factor is the ratio of real power to apparent power, typically between 0.8 and 1.0 for AC appliances.
How do you calculate 3-phase amps?▼
Amps = Watts / (1.732 * Voltage * Power Factor).
Is this tool free?▼
Yes, our electrical converters are 100% free and client-side.
Quick Reference & Conversion Table
| Appliance Power (W) | Voltage (V) | Current (Amps at PF=1.0) |
|---|---|---|
| 100 W | 120 V | 0.83 A |
| 600 W | 120 V | 5.00 A |
| 1,200 W | 120 V | 10.00 A |
| 1,800 W | 120 V | 15.00 A |
| 4,800 W | 240 V | 20.00 A |
⚠️ Common Pitfalls to Avoid
- •Forgetting power factor (PF) on inductive AC motor loads.
- •Using DC formula for 3-phase commercial electrical equipment.
💡 Practical Real-World Uses
- •Sizing home circuit breakers (15A or 20A) to prevent overloads.
- •Selecting inverter capacity for solar battery setups and RVs.
- •Planning commercial generator load distribution.
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