Watts to Amps Converter
Convert watts to amps (and kilowatts) using the power formula — for appliances, circuits, and electrical planning.
Introduction
Every electrical appliance has a power rating printed on it — usually in watts — but circuit breakers, extension cords, and wiring are rated in amps. That mismatch means anyone plugging in a space heater, checking if a generator can handle a load, or wiring a new circuit needs to convert between the two. The Watts to Amps Converter does that instantly, using the same power formula that electricians and engineers rely on.nnThis isn't a niche calculation — it's one of the most searched electrical conversions online, precisely because so many everyday decisions (will this trip the breaker? can this extension cord handle it? is this generator big enough?) depend on getting from watts to amps quickly and correctly.
What This Tool Does
This calculator takes two inputs — power in watts and voltage in volts — and returns the current in amps, along with the same power value converted to kilowatts for easy comparison against utility bills. It applies the fundamental power law formula (Amps = Watts ÷ Volts), which holds for standard resistive electrical loads like heaters, lights, and most household appliances.
How to Use
1. Find the power rating of your appliance or circuit, usually printed on a label or in the product manual, in watts.n2. Enter that value in the Power (Watts) field.n3. Enter the voltage of the circuit — 120V for standard US household outlets, 240V for large appliances like dryers and ranges — in the Voltage field.n4. Click Calculate to see the current draw in amps.n5. Compare the result against your circuit breaker's amp rating to check for overload risk (consult a licensed electrician for any safety-critical decision).
Worked Example
Example 1 — Space heater on a standard outlet: A 1,500-watt space heater on a 120-volt circuit.nCalculation: 1500 ÷ 120 = 12.5 amps.nResult: 12.5 amps — close to the maximum safe continuous load on a standard 15-amp breaker (80% rule: 12 amps), which is why space heaters often trip breakers when combined with other devices.nnExample 2 — Electric dryer on a 240V circuit: A 4,000-watt electric dryer on a 240-volt circuit.nCalculation: 4000 ÷ 240 = 16.67 amps.nResult: 16.67 amps — comfortably within a standard 30-amp dryer circuit.nnExample 3 — LED light bulb: A 10-watt LED bulb on a 120-volt circuit.nCalculation: 10 ÷ 120 = 0.083 amps.nResult: 0.083 amps — illustrating why dozens of LED bulbs can run on a single circuit without concern.nnExample 4 — Generator sizing: Checking if a 2,000-watt portable generator can power a 1,800-watt appliance at 120V.nCalculation: 1800 ÷ 120 = 15 amps required, compared to the generator's rated output.nResult: 15 amps — the calculation confirms current draw, but total wattage capacity (not just amps) is the limiting factor for generator sizing.
Formula & Logic
The formula used is: Amps = Watts ÷ Volts, derived from the fundamental power law, P = V × I (Power equals Voltage times Current), rearranged to solve for current: I = P ÷ V.nnThis relationship holds precisely for resistive loads — devices like heaters, incandescent bulbs, and toasters that convert electrical energy directly into heat or light with no significant power factor. Motors, some electronics, and other reactive loads can have a power factor that makes their actual current draw somewhat higher than this simple formula suggests, which is why the tool's content notes this limitation for those specific device types.
Common Use Cases
Home electrical safety: Checking whether plugging in a new appliance risks overloading a circuit breaker.nExtension cord selection: Verifying an extension cord's amp rating can safely handle a given device's current draw.nGenerator sizing: Estimating whether a portable or backup generator can supply enough current for essential appliances during an outage.nRV and boat electrical systems: Calculating current draw for 12V or 120V systems when planning battery or shore power capacity.nSolar and battery system design: Converting appliance wattage to amp-hour requirements for off-grid or backup power planning.nElectrical trade education: Teaching and verifying Ohm's law and power law relationships in electrical training.
Tips
Always double-check the voltage of the specific circuit you're working with rather than assuming — it's printed on the breaker or can be measured with a multimeter.nFor safety-critical decisions like circuit sizing or breaker selection, always consult a licensed electrician — this calculator is a planning and estimation tool, not a substitute for code compliance verification.nRemember the 80% rule: a circuit breaker's continuous safe load is typically 80% of its rated amperage (e.g., a 15-amp breaker safely handles about 12 amps continuously).nKeep in mind that this formula is for single-phase AC or DC circuits; three-phase electrical systems use a different formula involving a power factor and the square root of 3.
Frequently Asked Questions
Divide power in watts by voltage: Amps = Watts / Volts. For example, a 1,500-watt heater on a 120-volt circuit draws 1500 / 120 = 12.5 amps.
The formula comes from the power law: P = V x I, rearranged to I = P / V, where P is power in watts, V is voltage, and I is current in amps.
1500 watts at 120 volts equals 12.5 amps — a common calculation for space heaters and hair dryers on a standard US household circuit.
2000 watts at 240 volts equals 8.33 amps — this voltage is typical of large appliances like electric dryers and ranges.
Standard US household outlets are 120 volts. Larger appliances (dryers, ovens, some ACs) often run on 240 volts.
Circuit breakers and wiring are rated in amps, not watts. Knowing the amp draw tells you whether an appliance will overload a given circuit.
This calculator uses the direct power formula (P = VI), suitable for resistive loads like heaters and lights. Motors and some electronics have a power factor that can change the effective amp draw — consult an electrician for those cases.
Yes — rearrange the same inputs. Multiplying the amps result by the voltage returns the original wattage, since Watts = Volts x Amps.
15 amps at 120 volts equals 1,800 watts — the maximum continuous safe load is usually 80% of that, or 1,440 watts, per standard electrical code guidance.
This calculator gives the mathematical current draw for planning purposes, but circuit breaker sizing should always be confirmed by a licensed electrician against local electrical code.
It's the same power value converted to kilowatts (watts divided by 1,000), useful for comparing against utility bills, which are typically measured in kilowatt-hours.
Last updated: August 7, 2026