The Fahrenheit system has freezing point at 32°, and boiling point at 212°. Custom has it that zero degrees Farenheit was chosen as the lowest temperature then attainable, and 100°F as body temperature. There are 180 degrees between 'freezing point' and 'boiling point'.

The Rankine scale has the same size of degree as the Fahrenheit, but with its zero at absolute zero - so the 'boiling point' (212°F) is 671.67°R.

The temperture at which volumes etc. are defined in the Imperial system is 62°F

To convert a Fahrenheit temperature to centigrade, do the following:
a) Subtract 32
b) Multiply by 5
c) Divide by 9

Try it with 66°F - you should get 19°C. To convert C to F, just do it the other way round!