Convert Millijoules to Kilocalories
Convert Millijoules (mJ) to Kilocalories (kcal) instantly and accurately.
Conversion Formula
kcal = mJ × 2.390057361e-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 Kilocalories
A kilocalorie (kcal) - the food Calorie (capital C) on US and Canadian nutrition labels - is exactly 4,184 J. WHO recommends ~2,000-2,500 kcal/day for adults. Energy density of nutrients: fat 9 kcal/g, carbohydrate 4 kcal/g, protein 4 kcal/g, ethanol 7 kcal/g. Running at 10 km/h burns ~600-800 kcal/h. Standard free energy of ATP hydrolysis is approximately −7.3 kcal/mol (−30.5 kJ/mol). Pre-SI thermodynamic tables in the US and Japan use kcal/mol for reaction enthalpies. 1 kcal = 4,184 J = 4.184 kJ = 3.968 BTU = 1.163 Wh.
Quick Reference Table
| Millijoules (mJ) | Kilocalories (kcal) |
|---|---|
| 1 mJ | 2.39 × 10-7 kcal |
| 2 mJ | 4.78 × 10-7 kcal |
| 5 mJ | 1.195 × 10-6 kcal |
| 10 mJ | 2.39 × 10-6 kcal |
| 25 mJ | 5.975 × 10-6 kcal |
| 50 mJ | 1.195 × 10-5 kcal |
| 100 mJ | 2.39 × 10-5 kcal |