Appliance Wattage Calculator - Watts, Volts & Amps
Calculate a single appliance's wattage, voltage, or amperage using the Ohm's Law power formula (P = V × I), solving for whichever value you don't know.
Solve For
V
A
W
Wattage
600.00 W
How Appliance Wattage Is Calculated
This is a single-appliance electrical calculator based on Ohm's Law power formula: wattage equals voltage multiplied by amperage. It's the tool to reach for when a device's nameplate or label lists its amp draw but not its wattage — for example, many appliance labels only show a voltage and an amperage rating. Pick which value you want to solve for, enter the other two, and the missing value is calculated instantly.
Volts = Watts ÷ Amps
Amps = Watts ÷ Volts
Example
A label reading "120V, 5A" means the appliance draws 120 × 5 = 600 watts. Conversely, if you know an appliance is rated at 1500 watts on a standard 120-volt circuit, it draws 1500 ÷ 120 = 12.5 amps.
Common Use Cases
- Converting a nameplate's voltage and amperage rating into a wattage figure.
- Checking whether a single appliance will overload a circuit's amp rating.
- Working out the voltage a device needs given its known wattage and amp draw.
- Quick single-device power checks before buying a plug adapter or extension cord.
FAQs
How is this different from the LED Wattage Calculator?
The LED Wattage Calculator totals the combined power draw of many LEDs or an entire LED strip. This tool instead works with a single appliance and applies the basic Ohm's Law power formula (watts = volts × amps) to solve for whichever one of the three values you don't already know.
How is this different from the Inverter Size Calculator?
The Inverter Size Calculator adds up the wattage of a whole list of appliances to size a backup power inverter, including a safety margin. This tool is a simple single-appliance electrical calculation — useful for finding one appliance's wattage before adding it to an inverter sizing list.
Does this account for power factor on motor-driven appliances?
No — this uses the basic resistive-load power formula (watts = volts × amps), which is accurate for purely resistive loads like heaters and incandescent lighting. Motor-driven appliances have a power factor below 1, so their real wattage may be somewhat lower than volts × amps suggests.