Convert Btu to Joules (J)
1 Btu equals 1055.06 Joules.
Btu to Joule Converter
What Is a BTU?
The British Thermal Unit (BTU) is a unit of energy commonly used in heating, cooling, and energy content of fuels. One BTU is the amount of energy needed to raise the temperature of one pound of water by one degree Fahrenheit.
What Is a Joule?
The joule (J) is the SI unit of energy, defined as 1 newton·meter or 1 watt·second. It is used in physics, engineering, and nutrition (often as kilojoules, kJ).
BTU to Joules Formula
The conversion formula is:
joules = BTU × 1,055.06
The International Table BTU (BTUIT) equals 1,055.05585262 J. This value is derived from the thermochemical definitions of the BTU and the calorie.
Worked Example
Convert 100,000 BTU (1 therm of natural gas) to joules:
- Multiply: 100,000 × 1,055.06 = 105,506,000 J ≈ 105.5 MJ
Quick Estimation
1 BTU ≈ 1 kJ (actual: 1.055 kJ — within 5.5%). For rough calculations, BTU and kJ are nearly interchangeable.
Common Use Cases
- HVAC system ratings: Furnace output and AC capacity are rated in BTU/h in the US. Converting to watts (J/s) helps compare with metric-rated equipment.
- Natural gas billing: US gas bills use therms (100,000 BTU). One therm ≈ 105.5 MJ ≈ 29.3 kWh.
- Fuel energy content: Comparing energy density of fuels across imperial and SI systems. Gasoline: ~124,000 BTU/gallon ≈ 131 MJ/gallon.
- Engineering calculations: Converting between imperial and SI energy specifications in mechanical and thermal engineering.
Frequently Asked Questions
How many joules are in 1 BTU?
One International Table BTU equals 1,055.05585262 joules (approximately 1,055 J or 1.055 kJ). For quick estimates, 1 BTU ≈ 1 kJ.
What is the difference between BTU and BTU/h?
BTU is a unit of energy (like joules). BTU/h (BTU per hour) is a unit of power (like watts). An air conditioner rated at 12,000 BTU/h delivers 12,000 BTU of cooling per hour, which equals about 3,517 watts (3.5 kW) — often called "1 ton" of cooling.
Are there different types of BTU?
Yes. The International Table BTU (1,055.056 J) is the most common standard. The thermochemical BTU (1,054.350 J) is used in some scientific contexts. The difference is about 0.07% — negligible for most purposes.
How do I convert BTU to kWh?
Divide BTU by 3,412. Example: 100,000 BTU ÷ 3,412 = 29.3 kWh. This is useful for comparing gas and electricity costs.
Btu to Joules Conversion Table
Reference table with common btu to joules conversions. All values calculated with high precision.
Btu to Joules Table
1 to 100000
Joules to Btu Table
10000 to 1 × 109
Looking for the reverse? Convert Joule to Btu
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- Watts to Kilowatts — Power = energy ÷ time (1 W = 1 J/s)
