British thermal units to joules

Multiply British thermal units by 1,055.0559 to get joules.

1 BTU = 1,055.0559 JNIST SP 811

Convert

BTU

105,505.5853J

100 BTU = 105,505.5853 J

How to convert British thermal units to joules

The joule is the SI unit of energy, one newton-metre (one watt for one second). The British thermal unit is the (IT) British thermal unit, about 1055.06 joules.

Worked example — 100 BTU: 100 × 1,055.0559 = 105,505.5853 J.

British thermal units to joules table

Common conversions.
British thermal units	Joules
1 BTU	1,055.0559 J
5 BTU	5,275.2793 J
10 BTU	10,550.5585 J
50 BTU	52,752.7926 J
100 BTU	105,505.5853 J
500 BTU	527,527.9263 J
1,000 BTU	1,055,055.8526 J
5,000 BTU	5,275,279.2631 J
10,000 BTU	10,550,558.5262 J

Reverse and related

cal → J1 cal = 4.184 J J → cal1 J = 0.239006 cal kWh → J1 kWh = 3,600,000 J BTU → kWh1 BTU = 0.000293071 kWh kJ → J1 kJ = 1,000 J kcal → kJ1 kcal = 4.184 kJ

About British thermal units and joules

British thermal unit (BTU)

1 BTU = 1,055.0559 J

Definition. The (IT) British thermal unit, about 1055.06 joules

History and origin

The British thermal unit was defined as the heat needed to raise one pound of water by one degree Fahrenheit, making it the imperial counterpart of the calorie. It is about 1055 joules.

Current use

BTUs rate heating, air-conditioning and appliance output, especially in the United States.

Source: NIST SP 811, Appendix B; ISO 80000-5 (energy)

Joule (J)

1 J = 0.000947817 BTU

Definition. The SI unit of energy, one newton-metre (one watt for one second)

History and origin

The joule is the SI unit of energy, named after James Prescott Joule, who showed in the 1840s that heat and mechanical work are equivalent. It is the work done by one newton acting over one metre.

Current use

Joules are the standard energy unit in physics and appear on appliance and equipment ratings.

Source: NIST SP 811, Appendix B; ISO 80000-5 (energy)

Where people use this

British thermal units: heating and air conditioning, appliance ratings. Joules: physics, appliance ratings. 1 BTU is about 1055 J.

How we know this is right

The factor is fixed by the standards that define the units, not chosen — so it is exact, not a measurement:

1 J = 0.0009478171203 BTU, so 1 BTU = 1 ÷ 0.0009478171203 = 1,055.0559 J.

Every value is carried to full double precision; the display is rounded.

Both units are defined in NIST SP 811, Appendix B; ISO 80000-5 (energy).

Questions people ask

How many joules in a BTU?

One British thermal unit is about 1055 joules.

How many joules is 100 BTU?

100 BTU is about 105,506 joules.

What is a BTU?

A BTU is the heat needed to raise one pound of water by one degree Fahrenheit.

All British thermal unit conversions

British thermal units to kilowatt-hours1 BTU = 0.000293071 kWh