Convert energy units — joules, calories, kilowatt-hours, BTU, kilojoules.
| Unit | Name | Value |
|---|---|---|
| J | Joule | 1000 |
| cal | Calorie | 239.00574 |
| kcal | Kilocalorie (Cal) | 0.23900574 |
| kWh | Kilowatt-hour | 0.00027777778 |
| BTU | BTU | 0.94781339 |
Formula: Joule = Kilojoule × 1000
Multiply any kilojoule value by 1000 to get joule.
Reverse: Kilojoule = Joule × 0.001
Common kilojoule values — factor: 1 kJ = 1000 J
| Kilojoule (kJ) | Joule (J) | Context |
|---|---|---|
| 0.001 kJ | 1 J | 1 J |
| 0.01 kJ | 10 J | 10 J |
| 0.1 kJ | 100 J | 100 J |
| 1 kJ | 1,000 J | 1 kJ |
| 4.184 kJ | 4,184 J | 1 kcal |
| 10 kJ | 1e+04 J | 10 kJ |
| 100 kJ | 1e+05 J | 100 kJ |
| 1,000 kJ | 1e+06 J | 1 MJ |
| 3,600 kJ | 3.6e+06 J | 1 kWh |
| 1e+04 kJ | 1e+07 J | 10 MJ |
| 1e+05 kJ | 1e+08 J | 100 MJ |
| 1e+06 kJ | 1.000e+09 J | 1 GJ |
| 1e+08 kJ | 1.000e+11 J | 100 GJ |
| 1.000e+10 kJ | 1.000e+13 J | 10 TJ |
| 1.000e+12 kJ | 1.000e+15 J | 1 PJ |
kJ × 1,000 = J. Exact.
Simple kilo prefix.
J ÷ 1,000 = kJ.
Labels food energy in kJ for metric-market nutritional information.
Calculates reaction heat, enthalpy changes, and process energy in kJ.
Measures athlete metabolic rate and substrate oxidation in kJ.
Teaches heat transfer, steam tables, and engine cycles using kJ.
Prescribes energy intake using kJ in countries using metric labels.
Calculates heat duty for reactors, heat exchangers, and distillation in kJ.
The kilojoule (kJ) equals 1,000 joules and is the practical energy unit for food, chemistry, and heating applications in metric countries. Food energy labels in Australia, Europe, and most of the world use kilojoules.
A dietary calorie (kcal) equals 4.184 kJ. A can of soda contains about 600 kJ. The specific heat of water (4.184 kJ/kg·°C) means heating 1 liter of water by 1°C requires 4.184 kJ.
Interesting fact: An average adult needs about 8,000-10,000 kJ (2,000-2,400 kcal) per day. Running a marathon burns approximately 12,500 kJ.
The joule is the SI derived unit of energy, work, and heat, defined as the energy transferred when a force of one newton moves an object one meter. It was named after James Prescott Joule, the English physicist who established the mechanical equivalent of heat in the 1840s.
The joule is universal in physics and engineering: kinetic energy (½mv²), potential energy (mgh), electrical energy (VIt), and heat are all measured in joules. One joule is the energy needed to lift a 100g apple one meter against gravity.
Interesting fact: The human heart expends about 1 joule of energy with each beat. A 60-watt light bulb uses 60 joules every second. The entire energy released by a 1-megaton nuclear weapon equals about 4.18 × 10¹⁵ joules.
Converting kilojoule to joule is common across energy, nutrition, engineering, and science. Different sectors use different energy units — joules in physics, kcal in nutrition, kWh in electricity, and BTU in HVAC — making accurate conversion essential for cross-disciplinary work and international comparisons.
Quick reference: 5 kJ = 5000 J and 10 kJ = 10,000 J. Reverse: 1 J = 0.001 kJ. Exact factor: 1 kJ = 1000 J.
All conversions use IEEE 754 double-precision arithmetic, accurate to at least 8 significant figures.