kWh Calculator: Watts to Kilowatt-Hours
This kWh calculator converts watts into kilowatt-hours: kWh = watts × hours ÷ 1,000. Enter a device’s watts, the hours it runs per day and the number of days, and you get the energy it uses. Cost is a secondary line that starts from the U.S. average residential price of 18.16 cents per kWh (EIA, August 2026) and can be replaced with your own; to price an appliance by the hour, day, month and year, use the electricity cost calculator.
Maintained by Archie Chang · Price data retrieved November 8, 2026 · Methodology & sources
Your device
Optional. Clear the price box to hide the cost. The state figure is an average, not your rate.
Energy used
Energy used
15 kWh
100 W × 5 hours per day × 30 days ÷ 1,000
Cost is energy only. Your bill may add fixed charges, delivery charges and taxes.
This calculator shows energy in kilowatt-hours. For what a device costs to run per hour, day, month and year, use the electricity cost calculator. The state price is an EIA average, not your rate.
How to convert watts to kWh
kWh = watts × hours ÷ 1,000. A 100-watt bulb on for 5 hours a day for 30 days uses 100 × 5 × 30 ÷ 1,000 = 15 kWh.
Watts measure power at a moment; kilowatt-hours measure the energy used over time, which is what an electric bill charges for.
Watts to kWh table
Energy used at each wattage for one hour, 24 hours and 30 days of nonstop use. Multiply or divide for other run times.
| Watts | kWh in 1 hour | kWh in 24 hours | kWh in 30 days |
|---|---|---|---|
| 5 W | 0.005 | 0.12 | 3.6 |
| 10 W | 0.01 | 0.24 | 7.2 |
| 25 W | 0.025 | 0.6 | 18 |
| 60 W | 0.06 | 1.44 | 43.2 |
| 100 W | 0.1 | 2.4 | 72 |
| 250 W | 0.25 | 6 | 180 |
| 500 W | 0.5 | 12 | 360 |
| 750 W | 0.75 | 18 | 540 |
| 1,000 W | 1 | 24 | 720 |
| 1,200 W | 1.2 | 28.8 | 864 |
| 1,500 W | 1.5 | 36 | 1,080 |
| 1,800 W | 1.8 | 43.2 | 1,296 |
From kWh to dollars
Multiply kWh by your price per kWh. The calculator starts from EIA’s average residential price for the state you choose (August 2026; see electricity rates by state), and you can type the price from your bill. For a whole-month figure see the average electric bill page.
Frequently asked questions
How do you convert watts to kWh?
Multiply the watts by the hours the device runs, then divide by 1,000. A 100-watt bulb that stays on for 5 hours uses 100 × 5 ÷ 1,000 = 0.5 kWh.
How many kWh is 1,000 watts?
1,000 watts is 1 kilowatt. Running it for one hour uses 1 kWh, and running it for 24 hours uses 24 kWh.
Is a watt the same as a kWh?
No. A watt measures power, how fast a device uses energy. A kilowatt-hour measures energy, power over time, and it is the unit your electric bill is based on.
How do I turn kWh into dollars?
Multiply the kWh by your price per kWh. The calculator’s optional cost line starts from the average residential price for the state you pick (18.16 cents per kWh for the U.S. in August 2026, from EIA), but the price on your own bill is what counts.
Cite this page
Page title: kWh Calculator: Convert Watts to Kilowatt-Hours. Updated November 8, 2026. Canonical URL: https://fedratecalc.com/kwh-calculator/
Data source: EIA Electric Power Monthly, Table 5.6.A, compiled by FedRateCalc.
Plain-text citation
FedRateCalc. kWh Calculator: Convert Watts to Kilowatt-Hours. Updated November 8, 2026. https://fedratecalc.com/kwh-calculator/HTML link
<a href='https://fedratecalc.com/kwh-calculator/'>FedRateCalc</a>