235/45R18 tire size
A 235/45R18 tire stands 26.33 inches tall overall, on a 18-inch wheel, with a 105.8 mm sidewall and 235 mm of tread across. It turns roughly 766 times per mile.
- Overall diameter
- 26.33″
- 668.7 mm
- Sidewall height
- 105.8 mm
- 45% of 235 mm
- Circumference
- 82.7″
- 2,101 mm
- Revs per mile
- 766
- 476 per km
Reading the number
235 / 45 R 18 │ │ └─ rim diameter, 18 inches │ └──── aspect ratio, sidewall is 45% of width └──────── tread width, 235 mm sidewall = 235 × 0.45 = 105.75 mm diameter = (18 × 25.4) + (2 × 105.75) = 668.7 mm
Sizes that can replace 235/45R18
One rim step away, sorted by how close the rolling diameter stays.
Questions
›What does 235/45R18 mean?
235 is the tread width in millimetres. 45 is the aspect ratio, so the sidewall is 45% of 235 mm, or 105.8 mm. R means radial construction, and 18 is the wheel diameter in inches.
›How tall is a 235/45R18 tire?
26.33 inches, or 668.7 mm overall. That is the 18-inch rim plus a 105.8 mm sidewall at the top and another at the bottom.
›How many revolutions per mile does 235/45R18 do?
About 766 revolutions per mile, from a rolling circumference of 82.7 inches. Speedometers and odometers are calibrated against this figure, which is why changing size shifts both.
›What tires can replace 235/45R18?
Sizes within 3% of its rolling diameter and one rim step away, such as 215/55R17, 245/45R18, 225/50R17. Each is compared in full below.
Comparing against a size not listed? Open the calculator.