separately the coefficient of thermal expansion and the compressibility of the material, and compute the specific heat capacity at constant volume from these data according to the laws of thermodynamics. Units International system The SI unit for specific heat capacity is joule per kelvin per kilogram , J⋅K−1⋅kg−1. Since an increment of temperature of one degree Celsius is the same as an increment of one kelvin, that is the same as joule per degree Celsius per kilogram: J/(kg⋅°C). Sometimes the gram is used instead of kilogram for the unit of mass: 1 J⋅g−1⋅K−1 = 0.001 J⋅kg−1⋅K−1. The specific heat capacity of a substance (per unit of mass) has dimension L2⋅Θ−1⋅T−2, or (L/T)2/Θ. Therefore, the SI unit J⋅kg−1⋅K−1 is equivalent to metre squared per second squared per kelvin (m2⋅K−1⋅s−2). Imperial engineering units Professionals in construction, civil engineering, chemical engineering, and other technical disciplines, especially in the United States, may use English Engineering units including the pound (lb = 0.45359237 kg) as the unit of mass, the degree Fahrenheit or Rankine (°R = K, about 0.555556 K) as the unit of temperature increment, and the British thermal unit (BTU ≈ 1055.056 J), as the unit of heat. In those contexts, the unit of specific heat capacity is BTU/lb⋅°R, or 1 = 4186.68. The BTU was originally defined so that the average specific heat capacity of water would be 1 BTU/lb⋅°F. Note the value's similarity to that of the calorie - 4187 J/kg⋅°C ≈ 4184 J/kg⋅°C (~.07%) - as they are essentially measuring the same energy, using water as a basis reference, scaled to their systems' respective lbs and °F, or kg and °C. Calories In chemistry, heat amounts were often measured in calories. Confusingly, two units with that name, denoted "cal" or "Cal", have been commonly used to measure amounts of heat: the "small calorie" (or "gram-calorie", "cal") is 4.184 J, exactly. It was originally defined so that the specific heat capacity of liquid water would be 1 cal/°C⋅g. The "grand calorie" (also "kilocalorie", "kilogram-calorie", or "food calorie"; "kcal" or "Cal") is 1000 small calories, that is, 4184 J, exactly. It was defined so that the specific heat capacity of water would be 1 Cal/°C⋅kg. While these units are still used in some contexts (such as kilogram calorie in nutrition), their use is now deprecated in technical and scientific fields. When heat is measured in these units, the unit of specific heat