Convert Calories to Megajoules

Convert Calories (cal) to Megajoules (MJ) instantly and accurately.

Conversion Formula

MJ = cal × 4.184000000e-6

About Calories

A calorie (cal) - the thermochemical calorie - is exactly 4.184 J, defined as the heat to raise 1 g of water by 1°C. Standard since 1954. The calorie is the fundamental unit of heat measurement in thermochemistry: glucose combustion releases 669.9 kcal/mol; water vaporisation requires 539.7 cal/g. Bond dissociation energies in quantum chemistry are often quoted in kcal/mol. Note: the dietary Calorie (capital C) on food labels is 1 kcal = 4,184 J - a factor-of-1,000 difference that causes persistent confusion. 1 cal = 4.184 J = 1.163 × 10⁻³ Wh.

About Megajoules

A megajoule (MJ) is 10⁶ J - the scale of fuel combustion in vehicles and kinetic energy of road traffic. Energy content: 1 L diesel ~34.9 MJ; 1 L petrol ~32.2 MJ. A 1,500 kg car at 100 km/h has KE = ½ × 1,500 × 27.78² ≈ 0.579 MJ; at 200 km/h it carries 2.31 MJ - explaining crash severity's quadratic speed dependence. A 60 kWh EV battery stores 60 × 3.6 = 216 MJ. Detonation of 1 kg TNT releases 4.184 MJ. Adults at rest metabolise ~6-9 MJ/day. 1 MJ = 10⁶ J = 239.0 kcal = 0.27778 kWh = 947.8 BTU.

Quick Reference Table

→ Full Energy Converter