Energy Converter ⚡
Free online energy unit converter. Convert joules, calories, kWh, BTU, and 28+ energy units instantly. Includes J to cal, kWh to BTU calculator with formulas.
📐 Conversion Formula
Common Energy Conversions
Quick Energy Conversions
J to cal
× 0.239006
1 J = 0.239 cal
cal to J
× 4.184
1 cal = 4.184 J
kWh to BTU
× 3412.14
1 kWh = 3412 BTU
kWh to MJ
× 3.6
1 kWh = 3.6 MJ
Converter Performance Metrics
How to Use Energy Converter
Step 1: Enter Energy Value
Type the energy value you want to convert in the "From" field. The converter accepts any positive or negative number including decimals. For example, enter 1000 for 1000 joules or 10 for 10 kWh depending on your selected unit.
Step 2: Select Source Unit
Choose the unit of your input energy from the "From" dropdown. Options include joules, calories, kWh, BTU, kilojoules and 28+ other energy units. Select the unit that matches your measurement or specification.
Step 3: Select Target Unit
Pick the unit you want to convert to from the "To" dropdown. The conversion happens automatically in real-time as you change units. The formula used for conversion is displayed below for educational reference and verification.
Step 4: Use Results
View the converted result in the "To" field. Click Copy to copy the result to clipboard, Swap to reverse conversion direction, or Reset to start over. All calculations are instant and accurate for scientific applications.
Understanding Energy Units
What is Energy?
Energy is the capacity to do work or produce heat, measured in joules (J) in the SI system. Energy exists in many forms: kinetic, potential, thermal, chemical, electrical, and nuclear. The law of conservation of energy states energy cannot be created or destroyed, only converted between forms. One joule equals the work done by one newton of force over one meter.
Key Energy Relationships: \( E = mc^2 \) (mass-energy equivalence), \( E_k = \frac{1}{2}mv^2 \) (kinetic energy), \( E_p = mgh \) (gravitational potential energy). Common conversions: \( 1 \text{ J} = 0.239 \text{ cal} = 9.478 \times 10^{-4} \text{ BTU} \), \( 1 \text{ kWh} = 3.6 \text{ MJ} = 3412 \text{ BTU} \), \( 1 \text{ food Cal} = 1 \text{ kcal} = 4.184 \text{ kJ} \).
Common Energy Units Explained
Joule (J): SI unit of energy named after James Prescott Joule. One joule is energy transferred when one newton force moves object one meter. Also equals one watt-second. Common in physics and engineering. Prefixes: kilojoule (kJ) = 1,000 J, megajoule (MJ) = 1,000,000 J.
Calorie (cal): Energy needed to raise 1 gram of water by 1°C. Small calorie (cal) vs large Calorie (Cal) or kilocalorie (kcal) used in nutrition. Food labels show Calories (capital C) = 1,000 calories. One calorie = 4.184 joules. Important for chemistry, nutrition, and thermodynamics.
Kilowatt-hour (kWh): Energy consumed by 1,000-watt device running for one hour. Standard unit for electricity billing. One kWh = 3,600,000 joules = 3.6 MJ = 3,412 BTU. Average home uses 877 kWh/month (USA). Essential for understanding utility bills and energy consumption.
Common Use Cases
💡 Electricity & Utilities
Convert electricity consumption between kWh, MJ, and BTU for utility bills, solar panel output, and energy monitoring. Understand actual energy usage, compare rates across regions, calculate appliance costs. Essential for energy audits and reducing electricity expenses.
🍎 Nutrition & Diet
Convert food energy between Calories (kcal), kilojoules, and joules for nutrition labels, diet planning, and calorie counting. Different countries use different units—USA uses Calories, Australia uses kJ. Essential for fitness goals and understanding energy intake.
🔬 Physics & Science
Convert energy units for physics experiments, thermodynamics calculations, and scientific research. Calculate kinetic energy, potential energy, heat transfer, and work done. Essential for homework problems, laboratory reports, and understanding energy principles.
🏠 HVAC & Heating
Convert heating/cooling capacity between BTU, kWh, and therms for furnace ratings, air conditioner efficiency, and natural gas consumption. BTU common in USA, kW in Europe. Essential for sizing HVAC equipment and comparing fuel costs.
🔋 Battery & Storage
Convert battery capacity between Wh, kWh, and joules for phones, laptops, electric vehicles, and energy storage systems. Understand device runtime, charging requirements, and power bank capacity. Critical for comparing battery performance across products.
🏋️ Exercise & Fitness
Convert calories burned during exercise to kilojoules for fitness trackers and workout apps. Different regions show different units. Understand energy expenditure, compare workout intensities, and track fitness progress across international applications and devices.