Answer first
What this calculator tells you
Convert between joules, kilojoules, kilocalories, watt-hours, kilowatt-hours, BTU and foot-pounds. Compare a food label, an electric bill and a heating rating by putting them in one unit. Formula: Result = value × (from-unit factor ÷ to-unit factor), factors relative to joules. At the worked-example inputs, the converted value is 3,412.1. Holding every other input steady, moving value from 0.8 to 1.2 moves the result from 2,729.7 to 4,094.6.
Transparent method
The formula
Compare a food label, an electric bill and a heating rating by putting them in one unit.
Worked example
Example inputs
How to interpret the result
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.
At the worked-example inputs the converted value is 3,412.1. It rises with from and value and falls as to increases.
Conversion factors are exact defined constants; results are limited only by floating-point precision, not by real-world estimation.
Before you rely on it
What to check
Check which BTU is meant. The International Table BTU used here differs slightly from other definitions, though not enough to matter for household figures.
The common error
Where people go wrong with energy converter calculator
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.
Sensitivity evidence
How value changes the converted value
Holding every other input at the worked-example value, moving value from 0.8 to 1.2 moves the converted value from 2,729.7 to 4,094.6: a spread of 1,364.9, or 40% of the worked-example result.
| Value | 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 |
| 1worked example | 3,412.1 | 3,412.1 |
| 1.1 | 3,753.4 | 3,412.1 |
| 1.2 | 4,094.6 | 3,412.1 |
Every input, tested
Which input moves the converted value most
Of the 3 inputs, from moves the converted value most (0.00034 across the range tested) and value moves it least (682.4).
| Input | Tested from | To | Converted value at each end | Swing |
|---|---|---|---|---|
| From | Joules | Foot-pounds | 0.00095 to 0.00129 | 0.00034 (100%) |
| To | Joules | Foot-pounds | 3,600,000 to 2,655,223.7 | 944,776.3 (105506%) |
| Value | 0.9 | 1.1 | 3,070.9 to 3,753.4 | 682.4 (20%) |
Step by step
The worked example, input by input
| Input | Value used | What it means |
|---|---|---|
| Value | 1 | Enter the value used in this calculation. |
| From | Kilowatt-hours | Unit to convert from. |
| To | BTU (IT) | Unit to convert to. |
| Converted value | 3,412.1 | |
| 1 unit of "from" in "to" units | 3,412.1 | |
Inputs, definitions and assumptions
Value
Enter the value used in this calculation. The prefilled worked-example value is 1.
From
Unit to convert from. The prefilled worked-example value is Kilowatt-hours.
To
Unit to convert to. The prefilled worked-example value is BTU (IT).
How to use this calculator
- 1Verify the inputs. Gather value, from and to from your own documents; the prefilled values are examples.
- 2Save a baseline. The worked example puts the converted value at 3,412.1. Store your own version of it as Scenario A.
- 3Test one change. Start with from, the input with the biggest effect here: switching from changes the converted value: joules gives 0.00095; kilojoules gives 0.948; kilocalories (food calories) gives 4; watt-hours gives 3.4; kilowatt-hours gives 3,412.1; BTU (IT) gives 1.
- 4Check the boundary. Read the interpretation boundary above before acting on the result.
People also ask
Frequently asked questions
How do you calculate energy converter?
Result = value × (from-unit factor ÷ to-unit factor), factors relative to joules. At the worked-example inputs the converted value is 3,412.1.
What does the energy converter result mean?
Compare a food label, an electric bill and a heating rating by putting them in one unit. At the worked-example inputs the converted value is 3,412.1. It rises with from and value and falls as to increases.
How much does value change the converted value?
Holding every other input at the worked-example value, moving value from 0.8 to 1.2 moves the converted value from 2,729.7 to 4,094.6, a spread of 1,364.9.
What are the limits of this energy converter calculator?
Conversion factors are exact defined constants; results are limited only by floating-point precision, not by real-world estimation. The tables on this page test value only from 0.8 to 1.2; a value outside that range is not tabulated here.
Which input moves the converted value most in the energy converter calculator?
Ranked by how far each moves the converted value across the range tested: from (0.00034, 100%), to (944,776.3, 105506%) and value (682.4, 20%).
How much does from matter in the energy converter calculator?
The worked example uses Kilowatt-hours. With the other inputs left at the worked example, switching from changes the converted value: joules gives 0.00095; kilojoules gives 0.948; kilocalories (food calories) gives 4; watt-hours gives 3.4; kilowatt-hours gives 3,412.1; BTU (IT) gives 1.
How much does to matter in the energy converter calculator?
The worked example uses BTU (IT). Holding every other input at its worked-example value, switching to changes the converted value: joules gives 3,600,000; kilojoules gives 3,600; kilocalories (food calories) gives 860.4; watt-hours gives 1,000; kilowatt-hours gives 1; BTU (IT) gives 3,412.1.
Which inputs change the 1 unit of "from" in "to" units in the energy converter calculator?
At the worked-example inputs it is 3,412.1. From takes it from 0.00095 to 0.00129 and to takes it from 3,600,000 to 2,655,223.7.
Does a bigger tire diameter actually change my real speed?
Yes: a larger overall tire diameter covers more ground per wheel rotation. So your actual speed runs faster than your speedometer indicates (which is calibrated to the stock tire size), and your odometer under-reports distance traveled.
Why is a kilocalorie called a Calorie on food labels?
Food labels use the capital-C Calorie for a kilocalorie, which is 1,000 small calories. The energy converter treats kilocalories and food Calories as the same unit.
Sources and evidence
Free Calculators Online is independent and is not affiliated with or endorsed by the source organizations. Educational estimates only.