Electrical Conversion Calculators
Understanding the relationship between watts, amps, volts, and kilowatts is essential for calculating power consumption, sizing electrical systems, and understanding your electricity usage. Use our calculators below to convert between these units instantly.
Quick Conversion Calculators
Watts to Amps
Amps to Watts
Watts to Kilowatts
Kilowatts to Watts
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Understanding the Formulas
Watts = Amps × Volts
Power (watts) equals current (amps) multiplied by voltage (volts). This is known as the Power Formula or Watt's Law.
Example: 15 amps × 120 volts = 1,800 watts
Amps = Watts ÷ Volts
To find current (amps), divide power (watts) by voltage (volts).
Example: 1,500 watts ÷ 120 volts = 12.5 amps
1 Kilowatt = 1,000 Watts
Kilowatts are simply watts divided by 1,000. This larger unit is more convenient for expressing high power values.
Example: 5,000 watts = 5 kilowatts
Common Conversions Quick Reference
| Watts | Amps (120V) | Amps (240V) | Kilowatts |
|---|---|---|---|
| 100W | 0.83A | 0.42A | 0.1 kW |
| 500W | 4.17A | 2.08A | 0.5 kW |
| 1000W | 8.33A | 4.17A | 1.0 kW |
| 1500W | 12.5A | 6.25A | 1.5 kW |
| 2000W | 16.7A | 8.33A | 2.0 kW |
| 3000W | 25.0A | 12.5A | 3.0 kW |
| 5000W | 41.7A | 20.8A | 5.0 kW |
Understanding Voltage
In the United States and Canada, most household outlets provide:
- 120 volts - Standard outlets for most appliances
- 240 volts - Large appliances (dryers, ovens, AC units, electric water heaters)
European and many other countries use 220-240V as their standard voltage.
Practical Applications
Sizing Circuit Breakers
To determine what size breaker you need, divide watts by volts to get amps, then choose a breaker rated at least 125% of that value. For example, a 1,500-watt appliance on a 120V circuit draws 12.5 amps, so you'd want a 15-amp breaker minimum (preferably 20-amp for safety margin).
Generator Capacity
When sizing a generator, add up the wattage of all devices you plan to run simultaneously. A 5,000-watt (5 kW) generator can handle about 41.7 amps at 120V or 20.8 amps at 240V.
Understanding Your Electric Bill
Your utility company bills you in kilowatt-hours (kWh). One kWh is 1,000 watts used for one hour. A 100-watt light bulb running for 10 hours uses 1 kWh (100W × 10h = 1,000 Wh = 1 kWh).
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Frequently Asked Questions
How many watts in a kilowatt?
There are 1,000 watts in one kilowatt. The prefix "kilo" means 1,000, so 1 kW = 1,000 W.
How many amps is 1500 watts?
At 120 volts, 1,500 watts equals 12.5 amps (1500 ÷ 120 = 12.5). At 240 volts, it's 6.25 amps.
How many watts is 120 volts?
Voltage (volts) and power (watts) are different measurements. You need to know the current (amps) to calculate watts. At 120 volts with 1 amp, you have 120 watts. At 120 volts with 15 amps, you have 1,800 watts.
How many watts in an amp?
Amps and watts measure different things (current vs. power). The relationship depends on voltage. At 120V, 1 amp equals 120 watts. At 240V, 1 amp equals 240 watts.
Important Safety Notes
Warning: Never exceed the amperage rating of your circuits or outlets. Overloading can cause fires. Standard household circuits are typically rated for 15 or 20 amps. Always leave a safety margin and never use more than 80% of a circuit's rated capacity for continuous loads.
If you're unsure about electrical calculations or installations, always consult a licensed electrician.