245/40 R18 Tire Size Dimensions
A 245/40 R18 tire has an overall diameter of approximately 25.66 inches (652 mm).
How to use this tool
- Enter tire width, aspect ratio and rim diameter in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your overall diameter and the full breakdown beneath it.
245/40 R18 is a low-profile performance tire found on sports cars, luxury sedans, and hot hatches.
Frequently asked questions
- What does 205/55R16 mean?
- 205 is the tire width in mm, 55 is the aspect ratio (sidewall as % of width), and 16 is the rim diameter in inches. Sidewall height = 205 × 0.55 = 112.75 mm.