For each tire model, the tire diameter will vary. Most time dealer recommends to stay within 3% of the diameter/height of the original tire when changing the tire sizes. More than that you’ll get the risk of facing a brake failure.
The formula in getting the Tire Diameter is:
Tire Diameter = 2*(Tire Width / 25.4*) * (aspect ratio / 100 ) – (wheels size * -1)
By using the tire diameter calculator it will quickly calculate your tire diameter if you enter the aspect ratio, tire width (in mm), and the wheel size (in inches). You need to keep in mind that different brands have some differences in their tire sizes as well as used tires and those tires that have differing amount of wear.
Here’s How to Manually Calculate your vehicle Tire Diameter:
Example: Tire Size is 225 / 50R 16 using the equation.