Convert energy units — joules, calories, kilowatt-hours, BTU, kilojoules.
| Unit | Name | Value |
|---|---|---|
| kJ | Kilojoule | 0.001 |
| cal | Calorie | 0.23900574 |
| kcal | Kilocalorie (Cal) | 0.00023900574 |
| kWh | Kilowatt-hour | 2.7777778e-7 |
| BTU | BTU | 0.00094781339 |
Formula: Kilocalorie = Joule × 0.000239
Multiply any joule value by 0.000239 to get kilocalorie.
Reverse: Joule = Kilocalorie × 4184
Common joule values — factor: 1 J = 0.000239 kcal
| Joule (J) | Kilocalorie (kcal) | Context |
|---|---|---|
| 0.001 J | 2.390e-07 kcal | 1 mJ |
| 0.1 J | 2.390e-05 kcal | Heartbeat |
| 1 J | 0.000239 kcal | Lift apple 10cm |
| 4.184 J | 0.001 kcal | 1 calorie |
| 100 J | 0.0239 kcal | Sprinting 1 sec |
| 1,000 J | 0.239 kcal | 1 kJ |
| 4,184 J | 1 kcal | 1 kcal food |
| 1e+04 J | 2.39 kcal | 10 kJ |
| 1e+05 J | 23.9 kcal | 100 kJ |
| 1.055e+06 J | 252.2 kcal | 1 BTU |
| 3.6e+06 J | 860.4 kcal | 1 kWh |
| 1e+08 J | 2.39e+04 kcal | ~100 MJ |
| 1.000e+09 J | 2.39e+05 kcal | 1 GJ |
| 1.000e+12 J | 2.39e+08 kcal | 1 TJ |
| 1.000e+15 J | 2.390e+11 kcal | 1 PJ |
1 J = 0.000239 kcal. Memorize for instant estimates.
Use 0.000239 as a quick mental multiplier.
Multiply result by 4184 to recover the original J value.
Uses joules as the SI unit for all energy, work, and heat calculations.
Calculates kinetic energy, potential energy, and work in joules.
Measures reaction enthalpies, bond energies, and heat of solution in joules.
Converts between power (watts) and energy (joules = watt-seconds).
Measures fracture energy and impact resistance in joules.
Applies the first law of thermodynamics with energy in joules.
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.
The kilocalorie (kcal) equals 1,000 calories or 4,184 joules, and is the unit used on food labels worldwide (often written as 'Cal' with a capital C in the US). It was standardized by the International Table calorie in 1956.
Nutritionists, dietitians, and food scientists use kcal for daily energy intake recommendations. Most adults need 2,000–2,500 kcal/day. Exercise apps, fitness trackers, and dietary plans all operate on kcal.
Interesting fact: One gram of fat yields about 9 kcal, one gram of carbohydrate or protein yields about 4 kcal. A single sugar cube (4g) contains about 16 kcal.
Converting joule to kilocalorie 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 J = 0.001195 kcal and 10 J = 0.00239 kcal. Reverse: 1 kcal = 4184 J. Exact factor: 1 J = 0.000239 kcal.
All conversions use IEEE 754 double-precision arithmetic, accurate to at least 8 significant figures.