I am reading something about thermodynamics and everything are not given in SI units. In the material, they use Fahrenheit for temperature, BTU for heat, lb for mass and in^2 for area. Now I need to calculate something with the data given in those units, well, I need to apply equation for ideal case, to assure the result of my calculation makes sense, must I convert all unit to SI? I know ideal gas equation defined in Kelvin unit. Can I only convert the temperature to Kelvin while keeping others units unchanged ?