Energy Conversion Calculator

How it works

1. 1Enter the numeric energy value you want to convert.
2. 2Select the source unit in the “From” dropdown and the target unit in the “To” dropdown from the nine supported units.
3. 3The result appears instantly — the calculator multiplies by the source unit’s joule equivalent and divides by the target unit’s.

Use cases

• Electrical engineers converting kilowatt-hours to joules when sizing battery storage.
• Nutritionists converting dietary kilocalories (Calories) to kilojoules for food labels.
• Physics students converting between SI units (joules, electronvolts) and imperial units (BTU, foot-pounds).

Frequently asked questions

How many joules are in one kilowatt-hour?

One kilowatt-hour equals exactly 3,600,000 J (3.6 MJ), because 1 kWh = 1000 W × 3600 s. A 100 W bulb running 10 hours uses 1 kWh = 3,600,000 J.

What is the difference between a calorie and a kilocalorie?

A calorie (cal) is 4.184 J — the energy to raise 1 g of water by 1°C. A kilocalorie (kcal, the food Calorie) is 1000 cal = 4184 J. So a 200 kcal snack is 836,800 J.

How do BTU and joules relate?

1 BTU ≈ 1055 J — the energy to raise 1 pound of water by 1°F. For example, a 10,000 BTU air conditioner removes 10,000 × 1055 ≈ 10,550,000 J ≈ 2.93 kWh of heat per hour.