What is the price to income ratio on a car?

That would depend on how much money you make and how much the car costs.

The formula is: price paid for vehicle/ income.

A related question, and one possibly giving the answer desired is "what is the typical range of car price to annual income ratiOS".

1:2.5 is pretty average, with 1:1 and 1:6.1 the outer limits of a certain sample.

someone else wrote that 1:4 is a good ratio to aim for.