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: Kilowatt-Hour = Joule × 2.7778e-7
Multiply any joule value by 2.7778e-7 to get kilowatt-hour.
Reverse: Joule = Kilowatt-Hour × 3.6e+06
Common joule values — factor: 1 J = 2.7778e-7 kWh
| Joule (J) | Kilowatt-Hour (kWh) | Context |
|---|---|---|
| 0.001 J | 2.778e-10 kWh | 1 mJ |
| 0.1 J | 2.778e-08 kWh | Heartbeat |
| 1 J | 2.778e-07 kWh | Lift apple 10cm |
| 4.184 J | 1.162e-06 kWh | 1 calorie |
| 100 J | 2.778e-05 kWh | Sprinting 1 sec |
| 1,000 J | 0.0002778 kWh | 1 kJ |
| 4,184 J | 0.001162 kWh | 1 kcal food |
| 1e+04 J | 0.002778 kWh | 10 kJ |
| 1e+05 J | 0.02778 kWh | 100 kJ |
| 1.055e+06 J | 0.2931 kWh | 1 BTU |
| 3.6e+06 J | 1 kWh | 1 kWh |
| 1e+08 J | 27.78 kWh | ~100 MJ |
| 1.000e+09 J | 277.8 kWh | 1 GJ |
| 1.000e+12 J | 2.778e+05 kWh | 1 TJ |
| 1.000e+15 J | 2.778e+08 kWh | 1 PJ |
J ÷ 3,600,000 = kWh. Exact.
Divide by 3,600,000 — or divide by 1,000 to get kJ, then divide by 3,600.
3,600,000 J = 1 kWh, 3,600 J = 1 Wh.
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 kilowatt-hour (kWh) is the commercial unit of electrical energy, equal to the energy consumed by a 1,000-watt appliance in one hour (3,600,000 joules). It became standard with the growth of the electrical grid in the late 19th century.
Electricity bills worldwide are denominated in kWh. A typical household uses 300–1,000 kWh per month. An electric car uses about 15–25 kWh per 100 km. Solar panels generate 250–400 kWh per year per panel.
Interesting fact: The average price of electricity in the US is about $0.12 per kWh. One kWh can run a 100W light bulb for 10 hours, charge a smartphone about 100 times, or power a laptop for 2-3 days.
Converting joule to kilowatt-hour 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 = 1.3889e-6 kWh and 10 J = 2.7778e-6 kWh. Reverse: 1 kWh = 3.6e+06 J. Exact factor: 1 J = 2.7778e-7 kWh.
All conversions use IEEE 754 double-precision arithmetic, accurate to at least 8 significant figures.