Energy
J, cal, BTU, kWh
About This Calculator
Energy is the capacity to do work or produce heat. Joules are the SI unit, kilowatt-hours measure electricity consumption, BTUs are used for heating and cooling in the US, and calories (kcal) measure food energy in nutrition.
Formula
1 kcal = 4,184 J = 3.966 BTU
1 kWh = 3,600,000 J = 3,412 BTU = 860,420 cal
1 BTU = 1,055.06 J = 252 cal
Example Calculation
Convert 500 food Calories (kcal) to joules and kWh.
- Joules = 500 × 4,184 = 2,092,000 J
- kWh = 2,092,000 / 3,600,000 = 0.581 kWh
500 kcal = 2,092,000 J = 0.581 kWh
Energy Unit Equivalents
| Unit | Joules | kcal | BTU | kWh |
|---|---|---|---|---|
| 1 kWh | 3,600,000 | 860.4 | 3,412 | 1 |
| 1 kcal | 4,184 | 1 | 3.966 | 0.001163 |
| 1 BTU | 1,055 | 0.252 | 1 | 0.000293 |
| 1 MJ | 1,000,000 | 238.8 | 947.8 | 0.2778 |
Frequently Asked Questions
What is the difference between a calorie and a kilocalorie?
A food Calorie (with capital C) is actually a kilocalorie (kcal) = 1,000 small calories. When a food label says 200 Calories, it means 200 kcal or 200,000 small calories.
How many kWh does a typical home use per day?
A typical US household uses about 30 kWh per day (about 10,500 kWh per year). This varies greatly based on climate, home size, and appliances.
What is a BTU used for?
BTU (British Thermal Unit) is commonly used in the US for heating and cooling equipment ratings (HVAC), natural gas consumption, and air conditioner capacity. 1 BTU is the heat needed to raise 1 lb of water by 1°F.