Convert Millijoules to British Thermal Units
Convert Millijoules (mJ) to British Thermal Units (BTU) instantly and accurately.
Conversion Formula
BTU = mJ × 9.478171203e-7
About Millijoules
A millijoule (mJ) is 10⁻³ J - the scale of surgical lasers, spark ignition, and the kinetic energy of small everyday objects. Nd:YAG lasers for ophthalmology and tattoo removal deliver 10-200 mJ per pulse. The minimum spark energy to ignite methane-air is ~0.29 mJ; an automotive spark plug discharges 30-60 mJ per cycle. A 2 g mosquito flying at 1 m/s has kinetic energy ½ × 0.002 × 1² = 1 mJ. Electrocautery monopolar pulses deliver 50-500 mJ to coagulate blood vessels. 1 mJ = 10⁻³ J = 0.2390 cal.
About British Thermal Units
A British Thermal Unit (BTU) - the heat to raise 1 lb of water by 1°F - equals exactly 1,055.05585262 J. It dominates US HVAC: room air conditioners are rated in BTU/h (5,000-24,000 BTU/h = 1.5-7.0 kW); one ton of refrigeration is exactly 12,000 BTU/h. Natural gas is billed in therms (100,000 BTU) in the US. Higher heating values: natural gas ~1,020-1,050 BTU/ft³; No. 2 fuel oil ~138,700 BTU/US gal; propane ~91,500 BTU/US gal. 1 BTU = 1,055.06 J = 252.164 cal = 0.29307 Wh.
Quick Reference Table
| Millijoules (mJ) | British Thermal Units (BTU) |
|---|---|
| 1 mJ | 9.478 × 10-7 BTU |
| 2 mJ | 1.896 × 10-6 BTU |
| 5 mJ | 4.739 × 10-6 BTU |
| 10 mJ | 9.478 × 10-6 BTU |
| 25 mJ | 2.37 × 10-5 BTU |
| 50 mJ | 4.739 × 10-5 BTU |
| 100 mJ | 9.478 × 10-5 BTU |