Convert British Thermal Units to Kilocalories

Convert British Thermal Units (BTU) to Kilocalories (kcal) instantly and accurately.

Conversion Formula

kcal = BTU × 0.2521644007

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.

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.

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