all depends on the rolling radius of the wheel. best bet is to mark a point on the bottom of the tyre wall with some tape and another paralell mark on the floor, roll the car forward by hand until the tape is back facing the floor, then measure the distance, this gives the circumference but allows for some tyre deformation aswell. what gear the run was in, the gear ratio for that gear and your final drive if you can get me that info ill work it out for you.