BTUs to Millijoules Converter
Enter the energy in btus below to convert it to millijoules.
Convert BTUs to Millijoules
Enter a value in btus (BTU) to convert to millijoules (mJ).
British Thermal Unit to Millijoule Conversion Table
Table showing various british thermal unit measurements converted to millijoules. Click any preset value or arrow to load it into the converter.
| BTUs (BTU) | Millijoules (mJ) |
|---|---|
| 0.0000001 BTU | 0.1055056 mJ |
| 0.0000002 BTU | 0.2110112 mJ |
| 0.0000003 BTU | 0.3165168 mJ |
| 0.0000004 BTU | 0.4220223 mJ |
| 0.0000005 BTU | 0.5275279 mJ |
| 0.0000006 BTU | 0.6330335 mJ |
| 0.0000007 BTU | 0.7385391 mJ |
| 0.0000008 BTU | 0.8440447 mJ |
| 0.0000009 BTU | 0.9495503 mJ |
| 0.00000001 BTU | 0.0105506 mJ |
How to Convert BTUs to Millijoules
To convert btus to millijoules, multiply the energy by the following conversion ratio: 1,055,055.85262 millijoules/british thermal unit.
Since one british thermal unit is equal to 1,055,055.85262 millijoules, you can use this simple formula to convert:
The energy in millijoules is equal to the energy in btus multiplied by 1,055,055.85262.
For example, here's how to convert 5 btus to millijoules using the formula above.
How Many Millijoules Are in a British Thermal Unit?
There are 1,055,055.85262 millijoules in a british thermal unit, which is why we use this value in the formula above.
Our british thermal unit to millijoule calculator automatically converts your energy measurements with full decimal and scientific precision across US customary, imperial, and SI metric standards.
BTUs and millijoules are both units used to measure energy. Keep reading to learn more about each unit.
What Is a British Thermal Unit?
A british thermal unit is a unit of energy equal to 1,055.0558526 joules (J), the base unit for energy. Thermal energy unit equal to 1,055.056 Joules. [1]
The british thermal unit is classified as a US customary and imperial unit of energy. BTUs can be abbreviated as BTU; for example, 1 british thermal unit can be written as 1 BTU.
When working with btus (BTU) in formulas or technical specifications, always verify whether your target system uses SI metric, US customary, or British imperial standards.
In practice, btus (BTU) are widely used across large-scale industrial, bulk, and macro-level energy specifications within US customary and imperial workflows, engineering documentation, and technical data sheets.
What Is a Millijoule?
A millijoule is a unit of energy equal to 1/1,000 of a joule (0.001 J). One-thousandth of a Joule. [2]
The millijoule is classified as a metric and SI-compatible unit of energy. Millijoules can be abbreviated as mJ; for example, 1 millijoule can be written as 1 mJ.
In the metric system, "milli" is the standard SI prefix for thousandths, or 10⁻³. This makes the millijoule (mJ) a convenient decimal multiple of the joule (J).
In practice, millijoules (mJ) are widely used across fine-tolerance laboratory, analytical, and micro-scale energy measurements within SI metric workflows, engineering documentation, and technical data sheets.
When converting energy between btus (BTU) and millijoules (mJ), keep full floating-point precision (1 BTU = 1,055,055.85262 mJ; 1 mJ = 0.000000948 BTU) during intermediate calculations and round only the final millijoule figure to match your instrument tolerance.
More British Thermal Unit & Millijoule Conversions
Need to calculate in the opposite direction? Use our millijoules to btus calculator to switch your starting unit immediately. You can also explore related tools such as converting millijoules to btus, converting btus to joules, or converting btus to kilowatt-hours.
Frequently Asked Questions
References
- [1]NIST CODATA StandardNIST CODATA (CODATA Energy & Thermodynamic Constants)·Energy Metrology Standard — BTUs (BTU) to Millijoules (mJ)
- [2]NIST SP 811 SpecificationNIST SP 811 (NIST SP 811 App. B.9 (Energy, Work & Heat))·Unit Specifications: British Thermal Unit (BTU) (BTU) & Millijoule (mJ)
- [3]BIPM ReferenceBIPM (Derived SI Unit: Joule (J))·Conversion Factors & Mathematical Basis (BTU to mJ)