Energy Converter
Convert energy between J, kJ, cal, kcal, Wh, kWh, BTU units.
Input Information
Result
<strong>Energy Converter</strong> is a tool that provides accurate conversions between various energy units. You can quickly convert between joule (J), kilojoule (kJ), calorie (cal), kilocalorie (kcal), watt-hour (Wh), kilowatt-hour (kWh), and BTU, and it is used across science, engineering, medicine, and daily life.
Energy unit conversion is needed in food calorie calculations, home appliance power consumption comparisons, heat capacity design, fuel energy conversions, and more. It is particularly useful for preventing unit confusion when dealing with electricity bills, food nutrition labels, and boiler efficiency.
For students and researchers, it serves as learning material for thermodynamics. For facility and energy engineers and nutritionists, it is a practical tool. Accurate energy conversion is the first step toward cost savings and efficiency improvement.
Conversion coefficients follow international standards. 1 kcal = 4,184 J, 1 Wh = 3,600 J, 1 kWh = 3.6 MJ, 1 BTU ≈ 1,055 J. Note that the "Calorie" (capital C) on food labels is actually kcal (kilocalorie).
Term Glossary
- Calorie (Calorie vs cal)
- The capital "Calorie" on food nutrition labels is actually kcal (kilocalorie). Be careful not to confuse it with the lowercase "cal" (4.184 J) in thermodynamics, which differs by 1,000 times.
- Watt-hour (Wh)
- The amount of energy used by electrical power (W) for a certain time (h), where 1 Wh = 3,600 J. It is the basic unit for electricity bills and battery capacity calculations.
- BTU
- Abbreviation for British Thermal Unit, the heat required to raise 1 pound of water by 1°F (approx. 1,055 J). It is used in air conditioning and heating capacity specifications.
- Choose the input unit (J, kJ, kcal, Wh, kWh).
- Enter the value to convert.
- Choose the output unit.
- Press convert to see the result.
1 kWh Conversion
1 kWh = 3.6 MJ = approximately 860.4 kcal.
1 kcal Conversion
1 kcal = 4,184 J = 4.184 kJ.
1,000 J Conversion
1,000 J = 1,000 ÷ 4,184 ≈ 0.239 kcal.
Energy Unit Conversion Relationships
Energy Unit Conversion Relationships
Converting 2 kWh to kJ:
2 kWh × 3,600 = 7,200 kJ
Everyday Energy Comparisons
- Apple approx. 95 kcal, Lunch 600~800 kcal
- Adult male daily recommended intake 2,000~2,500 kcal
Power Consumption Comparison
- LED bulb (10 W, 8 hours) 80 Wh
- Air conditioner (1 kW, 8 hours) 8 kWh
- Electric vehicle battery 100 kWh for approx. 400 km driving
Fuel Energy Comparison
- Gasoline 1 L approx. 8,900 kcal (approx. 37,000 kJ)
- Diesel 1 L approx. 8,600 kcal, LPG 1 L approx. 5,900 kcal
Calorie Notation Caution
- Food "Calorie" (capital) is kcal.
- Do not confuse with thermodynamic "cal".
Electricity Bill Conversion
- Multiply kWh usage by unit price to calculate bills.
- Standby power also accumulates in kWh, so unplugging is effective.
BTU Usage
- Heating/cooling capacity is displayed in BTU/h.
- 1 BTU/h = 0.293 W, so unify units for comparison.
QWhat is the relationship between joules (J) and calories (cal)?
One calorie (cal) is about 4.184 joules (J). So 1 kcal = 1,000 cal = 4,184 J = 4.184 kJ. Conversely, 1 J is about 0.239 cal.
QWhat does kWh mean?
kWh (kilowatt-hour) is the energy consumed by a 1,000 W (1 kW) device running for 1 hour. 1 kWh = 3,600,000 J = 3.6 MJ, and it is commonly used for electricity billing.
QDo food calories (kcal) differ from physics calories (cal)?
Food labels use kilocalories (kcal). One food calorie = 1 kcal = 1,000 cal. So converting food energy to joules, 1 kcal = about 4,184 J.
QWhat is the difference between a watt (W) and a joule (J)?
A watt measures power (energy per unit time), while a joule measures energy (work). 1 W = 1 J/s, so multiplying watts by time gives energy in J or Wh.
QWhat are the conversion factors between energy units?
Key conversion factors are 1 kcal = 4,184 J, 1 cal = 4.184 J, 1 Wh = 3,600 J, 1 kWh = 3.6 MJ, and 1 BTU ≈ 1,055.06 J. Using these, any unit can be converted to another.