Energy Converter
Convert between joules, calories, BTU, kilowatt hours, and other energy units instantly.
How to Use the Energy Converter
- Enter Amount: Type the energy value you want to convert
- Select Input Unit: Choose your starting unit (joules, calories, BTU, etc.)
- Pick Output Unit: Select the unit you need for your result
- Read Result: The converted value displays automatically
- Switch Direction: Use the swap button to reverse the conversion
Energy Units Explained
Joules (J)
The joule is the SI unit for energy. One joule equals the energy transferred when applying a force of one newton over a distance of one meter. Physics and engineering calculations primarily use joules, kilojoules (kJ), or megajoules (MJ).
Calories (cal) and Kilocalories (kcal)
A calorie is the energy needed to raise one gram of water by one degree Celsius. Food labels show kilocalories (often written as "Calories" with a capital C). One food Calorie equals 1,000 small calories or about 4,184 joules.
BTU (British Thermal Unit)
BTU measures the energy required to heat one pound of water by one degree Fahrenheit. HVAC systems, furnaces, and air conditioners use BTU ratings. A typical home furnace might produce 80,000-100,000 BTU per hour.
Kilowatt-hours (kWh)
This unit measures electrical energy consumption over time. One kWh equals 1,000 watts used for one hour, or 3.6 million joules. Your electric bill charges per kWh. A typical American home uses about 900 kWh monthly.
Common Energy Conversions
Quick Reference
Everyday Examples
Practical Applications
Home and Daily Life
- Comparing electricity costs when evaluating appliances
- Calculating heating and cooling system efficiency (BTU ratings)
- Tracking food intake and exercise calories
- Sizing generators for backup power needs
Professional and Scientific
- Engineering thermodynamics and heat transfer calculations
- Nutrition science and dietary planning
- Physics experiments and energy efficiency studies
- Solar panel output and battery storage capacity
Frequently Asked Questions
What's the difference between energy and power?
Energy is the total amount of work done or heat transferred, measured in joules or kWh. Power is the rate at which energy is used or produced, measured in watts. A 100-watt bulb uses 100 joules of energy every second.
Why are food calories different from scientific calories?
Food labels show kilocalories (kcal), often written as "Calories" with a capital C. One food Calorie equals 1,000 small calories (cal). A snack with 200 Calories actually contains 200,000 calories or 200 kcal.
How do I calculate my home's energy costs?
Find your electricity rate (usually cents per kWh on your bill). Multiply the appliance wattage by hours used, divide by 1,000 to get kWh, then multiply by your rate. A 1,500W heater running 8 hours costs: (1,500 × 8 ÷ 1,000) × $0.12 = $1.44.
What BTU rating do I need for my air conditioner?
Calculate 20 BTU per square foot as a starting point. A 300 sq ft room needs about 6,000 BTU. Add 10% for sunny rooms, subtract 10% for shaded areas. Ceiling height, insulation, and climate also affect requirements.
Can I convert between mechanical and thermal energy units?
Yes, all energy units are interchangeable. One joule of mechanical energy equals one joule of thermal energy. However, converting energy between forms (like electricity to heat) involves efficiency losses in real-world applications.