Energy Converter for Joules, BTU, kWh, kJ and Calories

Convert an amount of energy between nine units, from electronvolts to kilowatt hours, and see it in all of them at once.

Runs in your browserFree, no sign-upLast reviewed October 8, 2026

Result

3600 kJ

Conversion details

Input: 1 kWh; Kilowatt hour (kWh)
Formula: 1 kWh = 3600 kJ
Rounded: 3,600 kJ

Same value in every unit

Unit	Value
Joule (J)	3600000 J
Kilojoule (kJ)	3600 kJ
Calorie (cal)	860420.650096 cal
Kilocalorie (kcal, food calorie)	860.42065 kcal
Watt hour (Wh)	1000 Wh
Kilowatt hour (kWh)	1 kWh
British thermal unit (BTU)	3412.141633 BTU
Foot-pound (ft·lb)	2655223.737398 ft·lb
Electronvolt (eV)	2.246943e+25 eV

Quick answers

How many joules are in a BTU?: One British thermal unit is 1,055.055853 joules, usually rounded to 1,055.06 J or 1.055 kJ. This is the International Table BTU, the most widely used definition. One joule is 0.000948 BTU.
How do I convert joules to BTU?: Divide the joules by 1,055.056, or multiply by 0.000947817. For example, 1,000 J is 0.947817 BTU, 10,000 J is 9.478171 BTU and 1,000,000 J is 947.81712 BTU.
How do I convert kJ to BTU?: Multiply kilojoules by 0.947817. So 1 kJ is 0.947817 BTU, 100 kJ is 94.781712 BTU and 1,000 kJ is 947.81712 BTU. In reverse, 1 BTU is 1.055056 kJ.
How many joules are in a kilowatt hour?: Exactly 3,600,000 joules, which is 3,600 kJ or 3.6 megajoules. A watt is one joule per second and an hour has 3,600 seconds, so 1,000 watts for one hour is 3,600,000 J. One joule is 0.000000277778 kWh.
Can I convert joules to kilowatts?: Not directly. Joules measure energy and kilowatts measure power, which is energy per second. One kilowatt is 1,000 joules per second, so divide joules by the number of seconds, then by 1,000. To get kilowatt hours instead, divide joules by 3,600,000.
How many joules is 1 unit of electricity?: On an electricity bill, one unit is one kilowatt hour, which is 3,600,000 joules or 3,600 kJ. It is also 3,412.141633 BTU and 860.42065 kcal.
How many kilojoules are in a kilocalorie?: One kilocalorie, the Calorie on food labels, is exactly 4.184 kJ. So 100 kcal is 418.4 kJ and a 2,000 kcal day is 8,368 kJ. One kilojoule is 0.239006 kcal.

About Energy Converter

This energy converter changes a value between joules, kilojoules, calories, kilocalories, watt hours, kilowatt hours, British thermal units, foot-pounds and electronvolts. The fixed points most people need are these: 1 BTU is 1,055.055853 joules, 1 kilojoule is 0.947817 BTU, 1 kilowatt hour is exactly 3,600,000 joules or 3,412.141633 BTU, and 1 kilocalorie is exactly 4.184 kilojoules. Every conversion goes through the joule, the SI unit of energy, and the result is shown to six decimal places with the factor for your chosen pair. It converts energy only. Kilowatts and BTU per hour are power, a rate of using energy, and need a time before they can be converted.

Joules to BTU conversion table

Joules (J)	BTU	BTU	Joules (J)
1	0.000948	1	1,055.055853
10	0.009478	5	5,275.279263
100	0.094782	10	10,550.558526
500	0.473909	100	105,505.585262
1,000	0.947817	1,000	1,055,055.85262
5,000	4.739086	5,000	5,275,279.2631
10,000	9.478171	10,000	10,550,558.5262
100,000	94.781712	12,000	12,660,670.23144
1,000,000	947.81712	100,000	105,505,585.262

The left pair converts joules to BTU and the right pair BTU to joules. The two halves of a row are not equal amounts.

Kilojoules to BTU and kWh, and BTU to kilojoules and kWh

Kilojoules are the practical size for heating, appliance and food energy figures.

Kilojoules	BTU	kWh	BTU	Kilojoules	kWh
1 kJ	0.947817	0.000278	1 BTU	1.055056	0.000293
10 kJ	9.478171	0.002778	100 BTU	105.505585	0.029307
100 kJ	94.781712	0.027778	1,000 BTU	1,055.055853	0.293071
300 kJ	284.345136	0.083333	5,000 BTU	5,275.279263	1.465355
500 kJ	473.90856	0.138889	10,000 BTU	10,550.558526	2.930711
1,000 kJ	947.81712	0.277778	12,000 BTU	12,660.670231	3.516853
3,600 kJ	3,412.141633	1	18,000 BTU	18,991.005347	5.275279
8,400 kJ	7,961.663811	2.333333	24,000 BTU	25,321.340463	7.033706
10,000 kJ	9,478.171203	2.777778	36,000 BTU	37,982.010694	10.550559

Columns 1 to 3 and columns 4 to 6 are separate conversions. 300 kJ of electricity is 0.083333 kWh, or 83.333333 Wh.

Kilowatt hours to kilojoules and BTU

kWh	Kilojoules	BTU
0.5	1,800	1,706.070817
1	3,600	3,412.141633
2	7,200	6,824.283266
5	18,000	17,060.708166
10	36,000	34,121.416331
30	108,000	102,364.248994
100	360,000	341,214.163313
1,000	3,600,000	3,412,141.633128

The nine energy units and their size in joules

Unit	Joules	What it is
Joule (J)	1	SI unit: one newton of force moved through one metre
Kilojoule (kJ)	1,000	1,000 joules; used on food labels in many countries
Calorie (cal)	4.184	Thermochemical calorie, roughly the heat to warm 1 g of water by 1 °C
Kilocalorie (kcal)	4,184	The food Calorie: 1,000 calories
Watt hour (Wh)	3,600	One watt for one hour; battery capacity
Kilowatt hour (kWh)	3,600,000	One kilowatt for one hour; the unit on electricity bills
British thermal unit (BTU)	1,055.055853	Roughly the heat to warm 1 lb of water by 1 °F
Foot-pound (ft·lb)	1.355818	One pound-force moved through one foot
Electronvolt (eV)	1.602177e-19	Energy gained by one electron crossing one volt

The tool stores the BTU as 1,055.05585262 J and the electronvolt as exactly 1.602176634 × 10^-19 J; the table shows them as the Result line prints them.

Joule to BTU formula and the general rule

BTU = joules ÷ 1,055.05585262. In general: target value = value × (joules per source unit) ÷ (joules per target unit)

Every unit has a fixed size in joules. Multiply your value by the source unit's joules, then divide by the target unit's joules. For 8,400 kJ to BTU: 8,400 × 1,000 = 8,400,000 J, and 8,400,000 ÷ 1,055.05585262 = 7,961.663811 BTU. For joules to kilowatt hours the divisor is 3,600,000, so 10,000,000 J is 2.777778 kWh.

Worked energy conversions

Joules to BTU

Value 5000, From Joule (J), To British thermal unit (BTU)

4.739086 BTU

The Formula line reads 1 J = 0.000948 BTU because it is cut to six decimals; the Result uses the full factor.

A heater's daily use in kilojoules

A 2 kW heater running 3 hours uses 6 kWh. Value 6, From Kilowatt hour (kWh), To Kilojoule (kJ)

21600 kJ

The same 6 kWh is 20,472.849799 BTU and 21,600,000 J.

A food label in kcal

Value 250, From Kilocalorie (kcal, food calorie), To Kilojoule (kJ)

1046 kJ

Going the other way, 8,700 kJ is 2,079.349904 kcal.

A gas bill in BTU

Value 100000, From British thermal unit (BTU), To Kilowatt hour (kWh)

29.307107 kWh

100,000 BTU is one therm. One million BTU is 293.07107 kWh.

Kilocalories to electronvolts

Value 1, From Kilocalorie (kcal, food calorie), To Electronvolt (eV)

2.611447e+22 eV

Very large and very small results are shown in scientific notation. One joule is 6.241509e+18 eV.

Energy versus power: kWh and kW, BTU and BTU per hour

A common reason a conversion looks wrong is mixing energy with power. Energy is a quantity: joules, kilowatt hours, BTU, calories. Power is how fast energy is used: watts, kilowatts, BTU per hour. One watt is one joule per second, so power multiplied by time gives energy.

Air conditioners and furnaces are labelled in BTU, but the rating is really BTU per hour. A 12,000 BTU unit moves 12,000 BTU of heat each hour. Converting 12,000 BTU here gives 3.516853 kWh, which means its cooling capacity is about 3.5 kW. That is the heat it moves, not the electricity it draws, which is typically a fraction of that.

The same care applies to electricity. A kilowatt hour is the energy used by a 1 kW load in one hour. To turn a wattage into energy, multiply by hours first: a 60 W lamp for 1 hour is 60 Wh, which converts to 216 kJ.

Two definitions are worth knowing. The BTU here is the International Table BTU of 1,055.05585262 J; the thermochemical BTU is about 1,054.35 J, a difference of under 0.1 percent. The calorie here is the thermochemical calorie of exactly 4.184 J; the International Table calorie is 4.1868 J.

How to get your result

1
Enter the amount of energy in the Value box.
2
Pick its unit in the From list, for example British thermal unit (BTU).
3
Pick the unit you need in the To list, for example Joule (J) or Kilowatt hour (kWh).
4
Read the Result and the Formula line, which gives the size of one source unit in the target unit.
5
Check the Same value in every unit table to read the figure in the other eight units.

Answers to common questions

How many BTU are in a kilowatt hour?

One kilowatt hour is 3,412.141633 BTU, commonly rounded to 3,412. One BTU is 0.000293 kWh, or 0.293071 watt hours. A 1 kW heater running for an hour therefore gives out about 3,412 BTU.

Is a food Calorie the same as a calorie?

No. The Calorie on nutrition labels is a kilocalorie, equal to 1,000 small calories or 4,184 joules. The small calorie is 4.184 joules. Choose Kilocalorie in the tool for anything from a food label.

Can I convert kelvin to joules?

Not with this tool, and not as a plain unit conversion. Kelvin measures temperature, not energy. Physicists relate the two with the Boltzmann constant: energy = 1.380649 × 10^-23 J per kelvin × temperature. At 300 K that is about 4.14 × 10^-21 J, or roughly 0.026 eV.

What is the difference between kWh and kJ?

Both measure energy; they differ only in size. One kilowatt hour is 3,600 kilojoules, and one kilojoule is 0.000278 kWh or 0.277778 watt hours. Electricity is billed in kWh, while science and food labelling use joules and kilojoules.

Does the converter include megajoules, therms or megawatt hours?

No. It has nine units: J, kJ, cal, kcal, Wh, kWh, BTU, ft·lb and eV. For megajoules divide a kilojoule result by 1,000, for megawatt hours divide kWh by 1,000, and for therms divide BTU by 100,000.

How many joules are in a foot-pound?

One foot-pound is 1.355818 joules, and one joule is 0.737562 foot-pounds. So 100 ft·lb is 135.581795 J. One BTU is 778.169262 foot-pounds.

Why is the electronvolt in an everyday converter?

It is the standard energy unit in atomic and particle physics, where joules are inconveniently large. One electronvolt is 1.602177 × 10^-19 J. The ionisation energy of hydrogen, 13.6 eV, converts to 2.178960e-18 J.

Why does the Rounded line show 0 for my result?

Rounded keeps two decimal places, so small values such as 1 J in BTU appear as 0 there. Use the Result line, which shows six decimals (0.000948 BTU) and switches to scientific notation below 0.000001.