Energy Converter
Convert energy values between joules, calories, watt-hours, and BTUs.. Use this smart bidirectional calculator to convert between different energy measurements instantly. See live results, calculation history, and exact formulas.
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Energy Converter
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Formula
kJ = J × 0.001
To convert Joule to Kilojoule, use the formula displayed above.
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How to Convert Energy Units
To perform a conversion, look up the target unit's conversion factor relative to the base unit (joule). Below are the exact mathematical formulas for the most common energy unit pairs:
Joule to Calorie
cal = J × 0.239005736 Kilowatt-hour to Joule
J = kWh × 3600000 Kilocalorie to Joule
J = kcal × 4184 BTU to Kilowatt-hour
kWh = BTU × 0.000293071 Energy Unit Conversion Charts
Here are the standard reference conversion charts displaying values from 1 to 20 for the most popular unit conversions:
J to cal
| J | cal |
|---|---|
| 1 | 0.239006 |
| 2 | 0.478011 |
| 3 | 0.717017 |
| 4 | 0.956023 |
| 5 | 1.195029 |
| 6 | 1.434034 |
| 7 | 1.67304 |
| 8 | 1.912046 |
| 9 | 2.151052 |
| 10 | 2.390057 |
| 11 | 2.629063 |
| 12 | 2.868069 |
| 13 | 3.107075 |
| 14 | 3.34608 |
| 15 | 3.585086 |
| 16 | 3.824092 |
| 17 | 4.063098 |
| 18 | 4.302103 |
| 19 | 4.541109 |
| 20 | 4.780115 |
kWh to J
| kWh | J |
|---|---|
| 1 | 3600000 |
| 2 | 7200000 |
| 3 | 10800000 |
| 4 | 14400000 |
| 5 | 18000000 |
| 6 | 21600000 |
| 7 | 25200000 |
| 8 | 28800000 |
| 9 | 32400000 |
| 10 | 36000000 |
| 11 | 39600000 |
| 12 | 43200000 |
| 13 | 46800000 |
| 14 | 50400000 |
| 15 | 54000000 |
| 16 | 57600000 |
| 17 | 61200000 |
| 18 | 64800000 |
| 19 | 68400000 |
| 20 | 72000000 |
kcal to J
| kcal | J |
|---|---|
| 1 | 4184 |
| 2 | 8368 |
| 3 | 12552 |
| 4 | 16736 |
| 5 | 20920 |
| 6 | 25104 |
| 7 | 29288 |
| 8 | 33472 |
| 9 | 37656 |
| 10 | 41840 |
| 11 | 46024 |
| 12 | 50208 |
| 13 | 54392 |
| 14 | 58576 |
| 15 | 62760 |
| 16 | 66944 |
| 17 | 71128 |
| 18 | 75312 |
| 19 | 79496 |
| 20 | 83680 |
BTU to kWh
| BTU | kWh |
|---|---|
| 1 | 0.000293 |
| 2 | 0.000586 |
| 3 | 0.000879 |
| 4 | 0.001172 |
| 5 | 0.001465 |
| 6 | 0.001758 |
| 7 | 0.002051 |
| 8 | 0.002345 |
| 9 | 0.002638 |
| 10 | 0.002931 |
| 11 | 0.003224 |
| 12 | 0.003517 |
| 13 | 0.00381 |
| 14 | 0.004103 |
| 15 | 0.004396 |
| 16 | 0.004689 |
| 17 | 0.004982 |
| 18 | 0.005275 |
| 19 | 0.005568 |
| 20 | 0.005861 |
Every Energy Unit, Explained
Energy conversion covers 8 units. Below is a plain-English definition of each one and where you'll actually meet it in daily life.
Joule (J)
The joule is the SI unit of energy — the work done by one newton over one meter.
Used for: Physics and engineering energy calculations.
Kilojoule (kJ)
A kilojoule is 1,000 joules.
Used for: Food-energy labels in many countries and technical energy measurements.
Calorie (cal)
A (small) calorie is the energy needed to raise one gram of water by one degree Celsius, exactly 4.184 joules.
Used for: Chemistry, nutrition science, and physical-activity calculations.
Kilocalorie (kcal)
A kilocalorie (Calorie, with capital C) is 1,000 small calories, exactly 4,184 joules.
Used for: Food energy labels — the 'Calories' on nutrition panels are kilocalories.
Watt-hour (Wh)
A watt-hour is one watt of power sustained for one hour, equal to 3,600 joules.
Used for: Battery capacities and small appliance energy consumption.
Kilowatt-hour (kWh)
A kilowatt-hour is 1,000 watt-hours — one kilowatt of power for one hour.
Used for: Electricity billing: the standard unit on household power bills worldwide.
BTU (BTU)
A British thermal unit (BTU) is the heat needed to raise one pound of water by one degree Fahrenheit, about 1,055 joules.
Used for: HVAC heating and cooling ratings, gas appliances, and barbecue grills.
Therm (therm)
A therm is 100,000 BTUs.
Used for: Natural-gas billing in the US and UK, and large-scale heating calculations.
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Energy Converter FAQs
What is a Energy converter?
A Energy converter is a free online utility that transforms a measurement expressed in one unit of energy into its equivalent in another, such as converting Joule to Kilojoule.
How do you convert energy units?
To convert energy units, choose your from-unit and to-unit from the dropdown list in the tool above, then enter the value you wish to convert. The tool computes the result live in real time using exact SI conversion factor formulas.
What are the most popular energy conversions?
The most frequently performed energy conversions on our site are Joule to Calorie, Kilowatt-hour to Joule, Kilocalorie to Joule. Our tool pre-calculates full charts and formulas for all of them.
Which energy units are supported?
We support all standard global SI (metric) and imperial units including Joule (J), Kilojoule (kJ), Calorie (cal), Kilocalorie (kcal), Watt-hour (Wh), Kilowatt-hour (kWh), and others.
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