How to Convert Energy Units
Convert between different energy units instantly. Our converter handles joules, calories, kilowatt-hours, BTU, and more-useful for physics, nutrition, heating/cooling, and electricity calculations.
Understanding Energy Units
Energy is the capacity to do work. Different fields use different units: joules (physics), calories (nutrition), kilowatt-hours (electricity), and BTU (heating/cooling). All measure the same thing in different contexts.
Common Energy Conversions
Key relationships: 1 calorie = 4.184 joules, 1 kilocalorie (food Calorie) = 1,000 calories = 4,184 joules, 1 kWh = 3.6 million joules, 1 BTU = 1,055 joules.
Example:
A 100-watt bulb running for 10 hours uses 1 kWh. A food Calorie (kcal) equals 4,184 joules of energy.
Common Use Cases
Real-world applications for this calculator
Nutrition
Understand food energy in calories (kcal) and how it relates to metabolic energy expenditure.
Electricity Bills
Calculate energy usage in kilowatt-hours to estimate electricity costs.
HVAC
Convert between BTU ratings and other units when sizing heating or cooling systems.
Tips
- Food energy: 1 food Calorie (kcal) = 4,184 joules.
- Electricity: watts × hours ÷ 1,000 = kWh.
- AC units: higher BTU = more cooling capacity. 20 BTU per square foot is a rough guide.
Frequently Asked Questions
What is the difference between a calorie and a Calorie?
A small calorie (cal) is the energy to raise 1g of water by 1°C. A food Calorie (Cal or kcal) equals 1,000 small calories. Food labels use Calories (kcal).
How do I convert kWh to joules?
Multiply kWh by 3,600,000 to get joules. 1 kWh = 3.6 × 10⁶ J. This is because 1 kWh = 1,000 watts × 3,600 seconds.
What is a BTU?
BTU (British Thermal Unit) is the energy needed to raise 1 pound of water by 1°F. It's commonly used for heating and cooling systems. 1 BTU ≈ 1,055 joules.
How much is 1 joule of energy?
One joule is a small amount of energy-about the energy needed to lift a small apple (100g) by one meter. It takes about 4.2 joules to heat 1 gram of water by 1°C.