245/40R18 tire size
A 245/40R18 tire stands 25.72 inches tall overall, on a 18-inch wheel, with a 98 mm sidewall and 245 mm of tread across. It turns roughly 784 times per mile.
- Overall diameter
- 25.72″
- 653.2 mm
- Sidewall height
- 98.0 mm
- 40% of 245 mm
- Circumference
- 80.8″
- 2,052 mm
- Revs per mile
- 784
- 487 per km
Reading the number
245 / 40 R 18 │ │ └─ rim diameter, 18 inches │ └──── aspect ratio, sidewall is 40% of width └──────── tread width, 245 mm sidewall = 245 × 0.40 = 98 mm diameter = (18 × 25.4) + (2 × 98) = 653.2 mm
Sizes that can replace 245/40R18
One rim step away, sorted by how close the rolling diameter stays.
Questions
›What does 245/40R18 mean?
245 is the tread width in millimetres. 40 is the aspect ratio, so the sidewall is 40% of 245 mm, or 98 mm. R means radial construction, and 18 is the wheel diameter in inches.
›How tall is a 245/40R18 tire?
25.72 inches, or 653.2 mm overall. That is the 18-inch rim plus a 98 mm sidewall at the top and another at the bottom.
›How many revolutions per mile does 245/40R18 do?
About 784 revolutions per mile, from a rolling circumference of 80.8 inches. Speedometers and odometers are calibrated against this figure, which is why changing size shifts both.
›What tires can replace 245/40R18?
Sizes within 3% of its rolling diameter and one rim step away, such as 225/50R17, 235/40R18, 215/55R17. Each is compared in full below.
Comparing against a size not listed? Open the calculator.