British thermal unit.
BTU to Joules Converter — BTU to J
Convert BTU (BTU) to Joule (J) using the exact conversion factor (1 btu = 1,055.055853 joule). See the formula, worked examples, conversion table, unit comparison, history, and common uses.
BTU to Joules converter
Converter
Energy Converter
Convert joules, calories, kilowatt-hours, BTU, electronvolts, therms, and mechanical work units.
Context values
Some unit families need one extra value for a physically accurate result.
The joule is the SI derived unit of energy.
Result = input x 1055.055853 / 1.
Energy uses the joule as the base unit.
Reserved above the conversion cards and below the converter.
About Converting BTU to Joules
BTU and Joule both measure energy, and the conversion is especially useful for comparing nutrition labels (kilocalories) against scientific energy figures (joules). BTU is typically associated with united States (HVAC, heating, and appliance energy ratings), while Joule is typically associated with standard scientific and engineering energy unit worldwide.
Formula
joules = btu × 1055.05585262
This factor comes from each unit's defined relationship to the category's base unit: 1 btu equals 1055.05585262 base units, and 1 joule equals 1 base unit, so dividing one by the other gives the direct btu-to-joule factor of 1055.05585262.
Simple example
1 BTU × 1055.055853 = 1,055.055853 J
1 btu = 1,055.055853 joules.
Real-world example
100 BTU × 1055.055853 = 105,505.5853 J
100 btu = 105,505.5853 joules.
Conversion table
| BTU (BTU) | Joule (J) |
|---|---|
| 1 BTU | 1,055.055853 J |
| 10 BTU | 10,550.55853 J |
| 100 BTU | 105,505.5853 J |
| 500 BTU | 527,527.9263 J |
| 1,000 BTU | 1,055,055.853 J |
| 2,000 BTU | 2,110,111.705 J |
Reverse conversion: Joule to BTU
1 J × 0.0009478171203 = 0.0009478171 BTU
1 joule = 0.0009478171 btu.
btu = joules × 0.000947817120313
For a page dedicated to this direction, see Joule to BTU.
BTU vs. Joule
| Aspect | BTU | Joule |
|---|---|---|
| Family | US customary unit | SI derived unit |
| Typical use | Air conditioner and furnace capacity ratings in the US | Physics and engineering energy calculations |
| Where it's used | United States (HVAC, heating, and appliance energy ratings) | Standard scientific and engineering energy unit worldwide |
Understanding the BTU
BTU (BTU) measures energy. A British thermal unit is defined as exactly 1,055.05585262 joules (the International Table BTU). It is classified as a US customary unit.
Where it's used: United States (HVAC, heating, and appliance energy ratings)
Uses of the BTU today
- Air conditioner and furnace capacity ratings in the US
- Water heater and appliance energy specifications
- US energy industry (natural gas is often billed via BTU content)
History of the BTU
The BTU originated in 19th-century steam engineering as the heat needed to raise one pound of water by one degree Fahrenheit, paralleling the calorie's metric definition. Several slightly different BTU values existed historically before the 'International Table' BTU was standardized at exactly 1,055.05585262 joules.
Historical origin. BTU was not the invention of a single named person; it developed through the process described above.
Understanding the Joule
Joule (J) measures energy. The joule is the SI derived unit of energy, defined as the work done by one newton acting over one meter. It is classified as a SI derived unit.
Where it's used: Standard scientific and engineering energy unit worldwide
Uses of the Joule today
- Physics and engineering energy calculations
- Electrical energy in scientific contexts (though kWh is used for billing)
- Nutrition labeling in some countries (alongside or instead of calories)
History of the Joule
The joule is named after English physicist James Prescott Joule, whose experiments in the 1840s established the mechanical equivalent of heat — demonstrating that mechanical work and heat are interchangeable forms of energy, foundational to the first law of thermodynamics.
The unit itself was formally adopted as the SI derived unit of energy by international agreement as part of the broader SI system, defined coherently from the base units (kg, m, s) rather than as an independent physical standard.
Historical origin. Joule was not the invention of a single named person; it developed through the process described above.
BTU — sources
- NIST Special Publication 811 — Documents the International Table BTU's exact joule equivalence.
Joule — sources
- BIPM SI Brochure — Coherent derived units — Defines the joule as the SI unit of energy.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many joules are in 1 btu?
1 btu equals 1,055.055853 joules, using the exact defined conversion factor rather than an estimate.
How do I convert btu to joule?
Multiply the btu value by 1055.055853. The converter above does this instantly to whatever precision you set.
How do I convert joule back to btu?
Use the reverse factor: 1 joule equals 0.0009478171 btu. You can also use the swap control in the converter above to flip the direction instantly.
What is a btu?
BTU (BTU) measures energy. A British thermal unit is defined as exactly 1,055.05585262 joules (the International Table BTU). It is classified as a US customary unit.
What is a joule?
Joule (J) measures energy. The joule is the SI derived unit of energy, defined as the work done by one newton acting over one meter. It is classified as a SI derived unit.
Is the btu to joule conversion exact?
Yes. A British thermal unit is defined as exactly 1,055.05585262 joules (the International Table BTU). That fixed definition is what the converter above uses, so any rounding you see is a display choice, not a limitation of the math.
Where is the btu still used today?
United States (HVAC, heating, and appliance energy ratings)