BTU/(lb·°R)

BTU per pound-Rankine

Specific heat capacityexact by definition

The BTU per pound-Rankine is exactly 4186.8 J/(kg·K), the same number as BTU/(lb·°F), because a Rankine degree and a Fahrenheit degree are the same size. It appears wherever a US calculation needs an absolute temperature, which is most of gas-cycle thermodynamics.

Watch out: Do not treat the °R and °F forms as different units needing a conversion between them. They differ only in which temperature scale the surrounding equation uses, and the specific heat number is identical.

1 BTU/(lb·°R) 4,186.8 J/(kg·K)