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Energy

J, kWh, BTU unit conversion

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System
J (Joule)
kJ (Kilojoule)
MJ (Megajoule)
Wh (Watt-hour)
kWh (Kilowatt-hour)
Ws (Watt-second)
cal (Calorie (thermochemical))
Cal (Calorie (food))
kcal (Kilocalorie)
BTU (British Thermal Unit)
thm (Therm)
eV (Electronvolt)
keV (Kiloelectronvolt)
MeV (Megaelectronvolt)
ft·lbf (Foot-pound force)
erg (Erg)
J
1000.00
kJ
1.00000
MJ
0.00100000
Wh
0.277778
kWh
0.000277778
Ws
1000.00
cal
239.006
Cal
0.239006
kcal
0.239006
BTU
0.947817
thm
0.00000947817
eV
6.24151e+21
keV
6.24151e+18
MeV
6.24151e+15
ft·lbf
737.562
erg
1.00000e+10

Conversion Formulas

J definition

W = F × d (1 J = 1 N·m = 1 kg·m²/s²)

J to cal

1 J = 0.239006 cal

J to kWh

1 J = 2.77778 × 10⁻⁷ kWh

J to BTU

1 J = 0.000947817 BTU

kWh to J

1 kWh = 3,600,000 J

cal to J

1 cal = 4.184 J

BTU to J

1 BTU = 1,055.06 J

eV to J

1 eV = 1.602 × 10⁻¹⁹ J

Reference Information

Power

Power (P) = Energy (E) / Time (t)

Work

Work (W) = Force (F) × Distance (d)

Kinetic Energy

Kinetic energy: KE = ½mv²

Potential Energy

Potential energy: PE = mgh

Food Calories

Food Calorie (Cal) equals kilocalorie (kcal)

Energy Units Guide

Joule (J)

SI base unit. Work done by 1 N force over 1 m distance

Calorie (cal)

Heat required to raise 1g of water by 1°C

Kilowatt-hour (kWh)

Unit of energy. Energy consumed by 1 kW for 1 hour

What is the Energy Converter?

A tool that converts between 11 different energy units in real-time, including Joule (J), kilowatt-hour (kWh), calorie (cal), BTU, and electron volt (eV). Enter a value to see conversion results for all units simultaneously.

  • Simultaneous conversion among 11 energy units
  • Adjustable decimal places
  • Conversion formulas and reference information
  • Support for electrical energy, heat, kinetic energy, and more
  • One-click result copying

How to Use

  1. 1

    Choose a Unit

    Choose the input unit for the energy you want to convert (J, kJ, kWh, cal, and others).

  2. 2

    Enter a Value

    Enter the energy value you want to convert.

  3. 3

    Review the Results

    The value is converted and displayed in 11 units at once.

  4. 4

    Adjust the Precision

    Set the number of decimal places to view results at the precision you need.

Frequently Asked Questions

The joule is the SI unit of energy, while the calorie is a unit of heat energy. 1 cal = 4.184 J.

No. The uppercase Calorie (Cal) used for food equals one kilocalorie (kcal), which is 1000 times a lowercase thermochemical calorie (cal).

The kilowatt-hour (kWh) is mainly used to calculate electricity charges. 1 kWh is the energy consumed by using 1000W of power for 1 hour.

A BTU (British Thermal Unit) is a unit of heat used in the United States and United Kingdom. It is the energy needed to raise 1 pound of water by 1°F. 1 BTU = 1055.06 J.

The electronvolt is used in atomic and nuclear physics to express extremely small amounts of energy. 1 eV = 1.602 × 10⁻¹⁹ J.

Tips & Best Practices

  • Use kWh when calculating electricity costs. Multiply an appliance's power consumption (W) by the time it is used.
  • Calories on food nutrition labels are measured in kcal. Multiply by 1000 to convert them to cal.
  • For physics problems, it is often easiest to calculate in the SI unit of joules (J).
  • Air-conditioner and heater capacity is often listed in BTU.
  • Increase the number of decimal places for more precise conversion results.

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