Convert Kilocalories to Gigajoules
Convert Kilocalories (kcal) to Gigajoules (GJ) instantly and accurately.
Conversion Formula
GJ = kcal × 4.184000000e-6
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.
About Gigajoules
A gigajoule (GJ) is 10⁹ J - the scale of fossil-fuel commodity volumes. One barrel of crude oil contains ~5.80 GJ; one metric tonne of hard coal ~29.3 GJ. Canadian energy bills express household consumption in GJ: average Canadian households use ~100-130 GJ/year. A 1 GW power plant at 33% efficiency burns ~10.9 GJ/h of fuel to generate 1 GWh = 3.6 GJ of electricity. Detonation of 1 tonne of TNT releases 4.184 GJ. 1 GJ = 10⁹ J = 277.78 kWh = 947,817 BTU = 9.4782 therms.
Quick Reference Table
| Kilocalories (kcal) | Gigajoules (GJ) |
|---|---|
| 1 kcal | 4.184 × 10-6 GJ |
| 2 kcal | 8.368 × 10-6 GJ |
| 5 kcal | 2.092 × 10-5 GJ |
| 10 kcal | 4.184 × 10-5 GJ |
| 25 kcal | 0.0001046 GJ |
| 50 kcal | 0.0002092 GJ |
| 100 kcal | 0.0004184 GJ |