Btu to Joule Converter
Free Btuto joule Converter for thermal & energy units. Enter a value to see equivalent measurements across systems. Free to use with no signup required.
Formula
Joules = BTU x 1055.06 | kWh = BTU / 3412.14 | cal = J / 4.184
Energy conversion uses the joule as the base SI unit. One BTU equals approximately 1055.06 joules. All energy units relate through fixed conversion factors: one calorie is 4.184 joules, one watt-hour is 3600 joules, and one foot-pound force is about 1.356 joules. The conversion multiplies by the source factor and divides by the target factor.
Worked Examples
Example 1: Furnace Energy Output
Problem: A furnace is rated at 80,000 BTU/h. How many joules and kilowatt-hours of energy does it produce per hour?
Solution: Joules = 80,000 x 1055.06 = 84,404,800 J = 84.4 MJ\nkWh = 80,000 / 3412.14 = 23.45 kWh\nAt $0.12/kWh equivalent, this equals $2.81/hour in energy output.
Result: 80,000 BTU = 84.4 MJ = 23.45 kWh
Example 2: Natural Gas Bill Conversion
Problem: A gas bill shows 75 therms used. Convert to BTU, megajoules, and kilowatt-hours.
Solution: BTU = 75 x 100,000 = 7,500,000 BTU\nMJ = 75 x 105.506 = 7,912.9 MJ\nkWh = 7,500,000 / 3412.14 = 2,198.2 kWh\nThis is typical monthly winter heating usage.
Result: 75 therms = 7.5 million BTU = 7,913 MJ = 2,198 kWh
Frequently Asked Questions
What is a BTU and how does it relate to joules?
A British Thermal Unit (BTU) is the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit at sea level. One BTU equals approximately 1055.06 joules. The BTU is still widely used in the US for HVAC systems, water heaters, and natural gas billing, while the rest of the world primarily uses joules and kilojoules. The joule is the SI unit of energy, defined as the work done by one newton of force over one meter.
Why are there different types of BTU?
Different BTU definitions exist because the specific heat of water varies slightly with temperature. The thermochemical BTU (1054.35 J) is based on thermochemical calorie definitions. The International Table BTU (1055.06 J) is the most commonly used and is based on the International Table calorie. The mean BTU (1055.87 J) averages over the 0-100 degree F range. For most practical purposes, the differences are less than 0.1% and the IT BTU is standard.
How do I convert BTU to kilowatt-hours?
To convert BTU to kilowatt-hours, divide by 3412.14 (since 1 kWh = 3412.14 BTU). To convert kWh to BTU, multiply by 3412.14. For example, a furnace rated at 100,000 BTU/h outputs about 29.3 kW of thermal energy. This conversion is essential for comparing the cost of heating with electricity versus natural gas, as electricity is billed in kWh and gas in therms (1 therm = 100,000 BTU).
What is a therm and how many BTU does it contain?
A therm is a unit of heat energy equal to exactly 100,000 BTU or approximately 105.5 megajoules. It is the standard billing unit for natural gas in the United States. One therm equals roughly 29.3 kilowatt-hours of energy. A typical US household uses about 50-100 therms of natural gas per month during winter for heating. The therm provides a convenient human-scale unit for measuring residential and commercial gas consumption.
How accurate are the results from Btu to Joule Converter?
All calculations use established mathematical formulas and are performed with high-precision arithmetic. Results are accurate to the precision shown. For critical decisions in finance, medicine, or engineering, always verify results with a qualified professional.
How do I get the most accurate result?
Enter values as precisely as possible using the correct units for each field. Check that you have selected the right unit (e.g. kilograms vs pounds, meters vs feet) before calculating. Rounding inputs early can reduce output precision.