Convert BTU per Pound-Rankine to Calories per Gram-Celsius

The BTU per Pound-Rankine (symbol: BTU/(lb·°R)) is a unit of specific entropy. An imperial specific-entropy unit equal to approximately 4,186.8 J/(kg·K) — numerically very close to (and traditionally used as numerically interchangeable with) the kJ/(kg·K) value, since BTU/(lb·°R) and kJ/(kg·K) have a conversion factor of exactly 4.1868 / 4.184 ≈ 1.0007 (a coincidence of imperial unit definitions). BTU/(lb·°R) is the dominant unit in US-edition steam tables (Keenan-Keyes-Hill, NIST/ASME Steam Tables US-customary printing), US-edition thermodynamics textbooks (Cengel-Boles, Moran-Shapiro-Boettner US editions; Borgnakke-Sonntag), ASHRAE Handbook tables (refrigerant data through 2024 edition still dual-lists), and US petroleum/refining process design per API and GPSA Engineering Data Book. Reference values: saturated liquid water at 70°F: s_f ≈ 0.0746 BTU/(lb·°R); saturated steam at 14.7 psia (1 atm boiling point): s_g ≈ 1.7567 BTU/(lb·°R); the entropy of vaporization at 1 atm s_fg ≈ 1.4446 BTU/(lb·°R). Convert BTU/(lb·°R) to kJ/(kg·K) by multiplying by 4.1868; the near-unity conversion is why dual-unit thermodynamics textbooks need only one decimal of precision to map between systems.

It belongs to the imperial measurement system.

BTU per Pound-Rankine are commonly used in turbine design, refrigeration analysis, and power plant engineering.

The Calorie per Gram-Celsius (symbol: cal/(g·°C)) is a unit of specific entropy. A CGS specific-entropy unit numerically identical to kcal/(kg·°C) and equal to 4,184 J/(kg·K) (using the thermochemical calorie). cal/(g·°C) appears in older chemistry literature for solution-calorimetry data (heats of dissolution, mixing, dilution), biological thermodynamics where the energy-scale is naturally small (protein unfolding ΔS ≈ 0.5 cal/(g·°C); ligand-receptor binding entropy in isothermal titration calorimetry; lipid-bilayer phase transitions), legacy food-science publications (specific heats of water = 1.000 cal/(g·°C) by historical definition), and pharmaceutical-formulation papers measuring excipient thermal properties via differential scanning calorimetry (DSC). The unit's persistence is due to the historical definition of the calorie as exactly the heat required to raise 1 g of water by 1 °C between 14.5°C and 15.5°C (giving water's specific heat the convenient value of 1.000 in this unit system). Mostly superseded by SI J/(kg·K) or kJ/(kg·K) in modern publications, but cal/(g·°C) still appears in NIST WebBook cross-references, in older Russian and German thermochemistry compilations (Landolt-Börnstein), and in TA Instruments and PerkinElmer DSC software output options.

It belongs to the metric measurement system.

Calories per Gram-Celsius are commonly used in turbine design, refrigeration analysis, and power plant engineering.