Convert Kilojoule to Joule
1 kilojoule = 1,000 joule (J). For example, 10 kilojoule = 10,000 joule and 100 kilojoule = 100,000 joule. Type any value below to convert kilojoule to joule both ways — it runs entirely in your browser.
Quick answer: Kilojoule to Joule
1 Kilojoule = 1,000 Joule (kJ → J). To convert kilojoule to joule, multiply by 1,000. To convert joule to kilojoule, multiply by 0.001. The converter at the top does this instantly and both ways; the sections below give the formula, worked examples, a full conversion chart and answers to the most common kilojoule-to-joule questions.
How to convert Kilojoule to Joule
To convert kilojoule to joule, multiply the number of kilojoule by the conversion factor 1,000, because 1 kJ = 1,000 J. The conversion is linear, so the same factor works for any value — whole numbers, decimals or fractions. For the reverse direction, 1 J = 0.001 kJ, so you divide by 1,000 (or multiply by 0.001) to turn joule back into kilojoule.
J = kJ × 1,000 ·
kJ = J × 0.001
- Write down the value you want to convert, in kilojoule.
- Multiply it by 1,000.
- The result is the same area/length/quantity expressed in joule.
Kilojoule to Joule — worked examples
Each row shows the exact arithmetic so you can follow the conversion step by step. For example, 5 kilojoule is 5,000 joule because 5 kJ × 1,000 = 5,000 J.
| Kilojoule | Calculation | Joule |
|---|---|---|
| 1 kJ | 1 kJ × 1,000 = 1,000 J | 1,000 J |
| 2 kJ | 2 kJ × 1,000 = 2,000 J | 2,000 J |
| 3 kJ | 3 kJ × 1,000 = 3,000 J | 3,000 J |
| 5 kJ | 5 kJ × 1,000 = 5,000 J | 5,000 J |
| 7 kJ | 7 kJ × 1,000 = 7,000 J | 7,000 J |
| 10 kJ | 10 kJ × 1,000 = 10,000 J | 10,000 J |
| 12 kJ | 12 kJ × 1,000 = 12,000 J | 12,000 J |
| 15 kJ | 15 kJ × 1,000 = 15,000 J | 15,000 J |
| 20 kJ | 20 kJ × 1,000 = 20,000 J | 20,000 J |
| 25 kJ | 25 kJ × 1,000 = 25,000 J | 25,000 J |
| 50 kJ | 50 kJ × 1,000 = 50,000 J | 50,000 J |
| 100 kJ | 100 kJ × 1,000 = 100,000 J | 100,000 J |
Common Kilojoule to Joule conversions
These are the kilojoule-to-joule values people look up most often. Every figure is computed from the exact factor, so you can rely on them for quick reference:
- 1 kilojoule = 1,000 joule
- 2 kilojoule = 2,000 joule
- 2.5 kilojoule = 2,500 joule
- 3 kilojoule = 3,000 joule
- 4 kilojoule = 4,000 joule
- 5 kilojoule = 5,000 joule
- 6 kilojoule = 6,000 joule
- 7 kilojoule = 7,000 joule
- 8 kilojoule = 8,000 joule
- 9 kilojoule = 9,000 joule
- 10 kilojoule = 10,000 joule
- 12 kilojoule = 12,000 joule
- 15 kilojoule = 15,000 joule
- 20 kilojoule = 20,000 joule
- 25 kilojoule = 25,000 joule
- 30 kilojoule = 30,000 joule
- 50 kilojoule = 50,000 joule
- 75 kilojoule = 75,000 joule
- 100 kilojoule = 100,000 joule
- 200 kilojoule = 200,000 joule
- 500 kilojoule = 500,000 joule
- 1000 kilojoule = 1,000,000 joule
Kilojoule to Joule conversion chart (both directions)
The chart below converts kilojoule to joule and joule to kilojoule side by side, so it works whichever way you need. 1 kilojoule = 1,000 joule, and 1 joule = 0.001 kilojoule.
| Kilojoule → Joule | Joule → Kilojoule |
|---|---|
| 0.25 kJ = 250 J | 0.25 J = 0.00025 kJ |
| 0.5 kJ = 500 J | 0.5 J = 0.0005 kJ |
| 1 kJ = 1,000 J | 1 J = 0.001 kJ |
| 2 kJ = 2,000 J | 2 J = 0.002 kJ |
| 3 kJ = 3,000 J | 3 J = 0.003 kJ |
| 4 kJ = 4,000 J | 4 J = 0.004 kJ |
| 5 kJ = 5,000 J | 5 J = 0.005 kJ |
| 6 kJ = 6,000 J | 6 J = 0.006 kJ |
| 7 kJ = 7,000 J | 7 J = 0.007 kJ |
| 8 kJ = 8,000 J | 8 J = 0.008 kJ |
| 9 kJ = 9,000 J | 9 J = 0.009 kJ |
| 10 kJ = 10,000 J | 10 J = 0.01 kJ |
| 12 kJ = 12,000 J | 12 J = 0.012 kJ |
| 15 kJ = 15,000 J | 15 J = 0.015 kJ |
| 20 kJ = 20,000 J | 20 J = 0.02 kJ |
| 25 kJ = 25,000 J | 25 J = 0.025 kJ |
| 30 kJ = 30,000 J | 30 J = 0.03 kJ |
| 40 kJ = 40,000 J | 40 J = 0.04 kJ |
| 50 kJ = 50,000 J | 50 J = 0.05 kJ |
| 75 kJ = 75,000 J | 75 J = 0.075 kJ |
| 100 kJ = 100,000 J | 100 J = 0.1 kJ |
| 150 kJ = 150,000 J | 150 J = 0.15 kJ |
| 200 kJ = 200,000 J | 200 J = 0.2 kJ |
| 250 kJ = 250,000 J | 250 J = 0.25 kJ |
| 500 kJ = 500,000 J | 500 J = 0.5 kJ |
| 1000 kJ = 1,000,000 J | 1000 J = 1 kJ |
Kilojoule vs Joule: which is bigger?
A kilojoule is the larger unit: one kilojoule equals 1,000 joules. Put another way, you need 1,000 joules to make a single kilojoule.
What is a Kilojoule? History, origin and usage
The kilojoule is simply 1,000 joules, formed with the SI “kilo” prefix, and it inherits the joule’s heritage from James Prescott Joule’s heat experiments. It became the practical everyday multiple of the joule because single joules are inconveniently small for food, fuel and exercise energy.
The kilojoule is the energy figure on nutrition labels across Europe, Australia and many other countries, usually printed alongside (or instead of) kilocalories. It is also handy for stating the energy of small chemical reactions, batteries and household tasks.
Australia and New Zealand use kilojoules almost exclusively for food energy, so a chocolate bar there is rated in kJ rather than Calories. One food “Calorie” (a kilocalorie) is about 4.184 kJ, which is why kilojoule figures on labels look roughly four times larger than the familiar calorie counts.
What is a Joule? History, origin and usage
The joule is named after the English physicist James Prescott Joule (1818-1889), a Salford brewer’s son who, through painstaking experiments in the 1840s, measured the mechanical equivalent of heat and showed that work and heat are interchangeable forms of energy. The name was proposed by Wilhelm Siemens at an 1882 British Association meeting, and the joule was adopted as an international unit at the 1889 International Electrical Congress — just weeks before Joule himself died.
As the SI unit of energy, the joule underpins all of physics and engineering, measuring mechanical work, heat and electrical energy alike (one joule is also one watt-second). It appears on European food labels (usually as kilojoules), in battery specifications, and anywhere energy must be stated in coherent SI units.
One joule is roughly the energy needed to lift a small apple (about 100 grams) one metre against gravity, or the kinetic energy of a 56-gram tennis ball travelling about 6 m/s. Because one joule equals one newton-metre, the joule is dimensionally identical to the newton-metre of torque, yet the two describe different physical quantities.
Convert 1 Kilojoule to other units
It can help to see a kilojoule next to the other units it is commonly compared with. One kilojoule (kJ) is equal to:
| 1 Kilojoule equals | Unit |
|---|---|
| 1,000 J | Joule |
| 1,000 N·m | Newton-metre |
| 0.001 MJ | Megajoule |
| 0.2777778 Wh | Watt-hour |
| 0.0002777778 kWh | Kilowatt-hour |
| 0.0000002777778 MWh | Megawatt-hour |
| 737.5621 ft·lbf | Foot-pound |
| 6,241,509,000,000,000 MeV | Megaelectronvolt |
| 239.0057 cal | Calorie |
| 0.2390057 kcal | Kilocalorie |
| 0.9478171 BTU | British Thermal Unit |
Convert 1 Joule to other units
One joule (J) is equal to:
| 1 Joule equals | Unit |
|---|---|
| 1 N·m | Newton-metre |
| 0.001 kJ | Kilojoule |
| 0.000001 MJ | Megajoule |
| 0.0002777778 Wh | Watt-hour |
| 0.0000002777778 kWh | Kilowatt-hour |
| 0.0000000002777778 MWh | Megawatt-hour |
| 0.7375621 ft·lbf | Foot-pound |
| 6,241,509,000,000 MeV | Megaelectronvolt |
| 0.2390057 cal | Calorie |
| 0.0002390057 kcal | Kilocalorie |
| 0.0009478171 BTU | British Thermal Unit |
Tips for converting Kilojoule to Joule
- To go from kilojoule to joule, multiply by 1,000; to go back, divide by 1,000 (or multiply by 0.001).
- For a quick mental estimate, remember that 1 kilojoule ≈ 1,000 joule, so 10 kilojoule ≈ 10,000 joule.
- The converter above keeps full precision; the tables round for readability, so use the tool for exact figures.
- Both fields update live as you type — change either side to convert in that direction.
How to use this Kilojoule to Joule converter
Type a number into the Kilojoule field and the equivalent in Joule appears instantly — there is no “convert” button to press and nothing is sent to a server, so it works offline once the page has loaded and is safe for any data. You can also type into the Joule field to convert the other way (joule to kilojoule). Use the swap control to flip the two units, and copy the result with a single click. Because the calculation runs in your browser with full floating-point precision, the converter is more exact than the rounded figures shown in the reference chart above — use the chart for quick look-ups and the tool for precise work.
Accuracy and method
Every figure on this page — the formula, the worked examples, the conversion chart and the “convert to other units” tables — is computed from a single verified conversion factor (1 kJ = 1,000 J), never copied from a hand-typed lookup table that could drift. That factor is derived from each unit’s definition in terms of a common base unit, and an automated check re-verifies all of the site’s factors on every update, so the numbers here stay correct over time. This matters for kilojoule-to-joule conversions because a small rounding error in a published table compounds quickly at larger quantities; computing from the exact factor avoids that.
Sources
- BIPM — The International System of Units (SI Brochure) — the defining document for the SI, published by the International Bureau of Weights and Measures. It fixes the base unit that this conversion resolves to, which is why the factor here can be exact rather than approximate.
- NIST — Definitions of the SI base units — the US National Institute of Standards and Technology reference for the SI base units, used here as an independent cross-check on the base-unit definition.
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Frequently asked questions
- How many joule are in 1 kilojoule?
- 1 kilojoule = 1,000 joule (J). To convert any number of kilojoule to joule, multiply by 1,000.
- How do I convert kilojoule to joule?
- Multiply the number of kilojoule by 1,000. For example, 10 kilojoule = 10 × 1,000 = 10,000 joule, and 25 kilojoule = 25,000 joule.
- How many kilojoule are in 1 joule?
- 1 joule = 0.001 kilojoule. So to convert joule back to kilojoule, multiply by 0.001.
- What is the formula to convert kilojoule to joule?
- joule = kilojoule × 1,000. The reverse formula is kilojoule = joule × 0.001.
- How much is 100 kilojoule in joule?
- 100 kilojoule = 100,000 joule. (And 1000 kilojoule = 1,000,000 joule.)
- Which is bigger, a kilojoule or a joule?
- A kilojoule is larger: 1 kilojoule = 1,000 joule.
- Is this kilojoule to joule converter accurate?
- Yes — every value is computed from the exact 1,000 J per kJ factor (not rounded look-up tables), and the factors are re-verified automatically on every update.
- Can I convert joule to kilojoule too?
- Yes. The converter works both ways — enter a value in either field. 1 joule = 0.001 kilojoule.