Need to know if a new appliance will trip your breaker? Our free watts to amps converter gives you the answer in one second. Electrical circuits are protected by breakers rated in amperes (amps). But most appliances only list wattage on their label. This tool converts watts to amps for any circuit voltage so you can prevent dangerous overloads.
Current Draw
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Recommended Breaker Size
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NEC 80% Safe Load
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How to Use This Watts to Amps Converter
Enter the wattage of your device. You can find this on the label on the back or bottom of almost any appliance. Next, select your circuit voltage from the dropdown. Standard US wall outlets are 120V. Large appliances like dryers, ranges, and Level 2 EV chargers use 240V outlets. Then click convert.
The calculator also tells you the recommended breaker size. Because the National Electrical Code (NEC) requires breakers to be sized at 125% of a continuous load, you need a larger breaker than the bare minimum amps your device draws.
Watts to Amps Formula Explained
The formula for a single-phase AC circuit (what you have in your home) is:
Amps (A) = Watts (W) ÷ Volts (V)
This comes directly from Ohm's Law and the basic power equation P = V × I, rearranged to solve for current (I). For a 1,200W space heater plugged into a standard 120V outlet: 1,200 ÷ 120 = 10 amps. A 15-amp breaker covers it with headroom to spare.
Watts to Amps Conversion Examples
Microwave (1,100W @ 120V): 9.2 amps — fits on a 15A circuit
Space Heater (1,500W @ 120V): 12.5 amps — needs a dedicated 15A or 20A circuit
Hair Dryer (1,800W @ 120V): 15 amps — right at the limit of a 15A breaker
EV Level 2 Charger (7,200W @ 240V): 30 amps — requires a dedicated 40A circuit
Central AC (3,500W @ 240V): 14.6 amps — needs a 20A double-pole breaker
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Tips for Electrical Safety in 2026
Never exceed 80% of breaker capacity. The NEC 80% rule isn't optional — it's code. Running a circuit above 80% of its rated capacity is a fire hazard.
Use dedicated circuits for heavy appliances. Space heaters, microwaves, and refrigerators should each be on their own circuit, not shared with other devices.
Check wire gauge, not just breaker size. A 20-amp breaker requires 12-gauge wire. Using 14-gauge wire behind a 20-amp breaker is a code violation and a fire risk.
Get a GFCI outlet in wet areas. Kitchens, bathrooms, garages, and outdoor outlets must be GFCI protected per NEC code.
Frequently Asked Questions
How do I convert watts to amps?
Divide the wattage by the voltage. Amps = Watts ÷ Volts. For a 1,200W device on a standard US 120V circuit: 1,200 ÷ 120 = 10 amps.
What voltage do US outlets use?
Standard US household outlets are 120 volts AC (single phase). Large appliances like dryers, ovens, and EV chargers use 240V outlets (double pole). Some older homes may have 110V wiring.
How many watts can a 15-amp circuit handle?
At 120V, a 15-amp circuit can handle up to 1,800 watts (15A × 120V = 1,800W). However, the NEC 80% rule limits continuous loads to 1,440 watts to prevent tripped breakers and overheating.
Why do I need to convert watts to amps?
Electrical circuits are protected by breakers rated in amps. To know whether a device will trip a breaker, you need to convert its wattage to amps and compare it to the breaker's rating. This is essential for safely adding high-draw appliances or EV chargers.
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