Enter the value and choose from joules, kilojoules, kilocalories, watt-hours, kilowatt-hours, BTU and foot-pounds. Take the value from an electric bill in kilowatt-hours, a food label in kilocalories, or a heater or furnace rating in BTU. One kilowatt-hour equals 3.6 million joules, and a food Calorie is a kilocalorie.
Use the same unit for energy, not power: a kilowatt measures the rate of using energy.
Energy Converter: worked example
| Energy to convert | 1 |
|---|---|
| Starting unit | Kilowatt-hours |
| Requested unit | BTU (IT) |
| Converted value | 3,412.1 |
| 1 unit of "from" in "to" units | 3,412.1 |
Energy Converter: formula
Common error: Confusing the food Calorie with the small calorie. A food Calorie is a kilocalorie, a thousand times the small one, and mixing them is a thousandfold error.
Energy and power are different: watts and kilowatts are rates, and kilowatt-hours are amounts. Efficiency matters in practice, since a furnace at 95% efficiency delivers less than its fuel's rating. BTU has several slightly different definitions, and the tool uses the international table value.
Units for heating and cooling capacity, such as tons, are not included.
Energy Converter: changing Energy to convert
| Energy to convert | Converted value | 1 unit of "from" in "to" units |
|---|---|---|
| 0.8 | 2,729.7 | 3,412.1 |
| 0.9 | 3,070.9 | 3,412.1 |
| 1 (example) | 3,412.1 | 3,412.1 |
| 1.1 | 3,753.4 | 3,412.1 |
| 1.2 | 4,094.6 | 3,412.1 |
Energy Converter: compare input ranges
| Input | Tested from | To | Converted value: low input | Converted value: high input | Swing |
|---|---|---|---|---|---|
| Starting unit | Joules | Foot-pounds | 0.00095 | 0.00129 | 0.00034 (100%) |
| Requested unit | Joules | Foot-pounds | 3,600,000 | 2,655,223.7 | 944,776.3 (105506%) |
| Energy to convert | 0.9 | 1.1 | 3,070.9 | 3,753.4 | 682.4 (20%) |
Energy Converter: individual input comparisons
| Input | Value | Converted value | 1 unit of "from" in "to" units |
|---|---|---|---|
| Energy to convert | 0.8 | 2,729.7 | 3,412.1 |
| 0.9 | 3,070.9 | 3,412.1 | |
| 1 | 3,412.1 | 3,412.1 | |
| 1.1 | 3,753.4 | 3,412.1 | |
| 1.2 | 4,094.6 | 3,412.1 | |
| Starting unit | Joules | 0.00095 | 0.00095 |
| Kilojoules | 0.948 | 0.948 | |
| Kilocalories (food Calories) | 4 | 4 | |
| Watt-hours | 3.4 | 3.4 | |
| Kilowatt-hours | 3,412.1 | 3,412.1 | |
| BTU (IT) | 1 | 1 | |
| Foot-pounds | 0.00129 | 0.00129 | |
| Requested unit | Joules | 3,600,000 | 3,600,000 |
| Kilojoules | 3,600 | 3,600 | |
| Kilocalories (food Calories) | 860.4 | 860.4 | |
| Watt-hours | 1,000 | 1,000 | |
| Kilowatt-hours | 1 | 1 | |
| BTU (IT) | 3,412.1 | 3,412.1 | |
| Foot-pounds | 2,655,223.7 | 2,655,223.7 |
Energy Converter: which assumptions move the result?
Energy Converter: values and definitions
| Quantity and definition | Value used |
|---|---|
| Energy to convert | 1 |
| Starting unit — Unit to convert from. | Kilowatt-hours |
| Requested unit — Unit to convert to. | BTU (IT) |
| Converted value | 3,412.1 |
| 1 unit of "from" in "to" units | 3,412.1 |
Unit Conversion calculators: Pressure Converter Calculator, Power Converter Calculator, Height Converter Calculator, Angle Converter Calculator, Data Rate Converter Calculator, Force Converter Calculator.
Energy shows up in different units depending on where you look: joules in science, kilocalories on food labels, kilowatt-hours on the electric bill, BTU on furnaces. They measure the same thing. One kilowatt-hour is 3.6 million joules, about 3,412 BTU and roughly 860 food Calories, so a snack and a heater rating can be compared directly once both are in one unit.
Reference values: one food Calorie is 4.184 kilojoules, one kilowatt-hour is 3.6 megajoules, and one BTU is about 1.055 kilojoules. A 2,000 Calorie diet is about 8.4 megajoules, or roughly 2.3 kilowatt-hours. The EPA counts a gallon of gasoline as 33.7 kilowatt-hours when it rates electric cars in miles per gallon equivalent, and a 100 watt bulb left on for ten hours uses exactly 1 kilowatt-hour, or 3.6 megajoules.
Check which BTU is meant. The International Table BTU used here differs slightly from other definitions, though not enough to matter for household figures.
Convert power on the power converter, temperature on the temperature converter, and pressure on the pressure converter. The watts to amps and voltage drop calculators cover electric loads, and the calories burned page uses food energy. The degree days calculator relates heating energy to weather.
Can I enter a furnace’s BTU-per-hour rating directly as BTU?
Only after multiplying by an operating duration in hours. A rate is not an amount of energy. Delivery efficiency and cycling can also change the heat delivered.
Does one kilocalorie equal one food Calorie?
Yes under the thermochemical energy convention used here: one kilocalorie is 4184 joules. A lowercase small calorie is one thousandth of that amount.
How many BTU are in a kilowatt-hour?
About 3,412 BTU. One kilowatt-hour equals 3.6 million joules.
Is a food Calorie the same as a calorie?
A food Calorie, written with a capital C, equals a kilocalorie, or 1,000 small calories, about 4,184 joules.
What is the difference between kW and kWh?
A kilowatt is a rate of using energy, and a kilowatt-hour is the amount used when running one kilowatt for an hour.