Rankine is a temperature scale that, like kelvin, sets zero at absolute zero, but uses Fahrenheit degrees. A difference of 1 degree R. is equal to a difference of 1 degree F, but absolute zero is 0 degrees R, or -459.67 degrees F. Thus:
To convert from Fahrenheit to Rankine, add 459.67.
To convert from Rankine to Fahrenheit, subtract 459.67.
To convert from kelvin to Rankine, multiply by 1.8.