315/40R18 tire size
A 315/40R18 tire stands 27.9 inches tall and 12.4 inches wide, with a 5.0-inch sidewall on an 18-inch rim.
- Overall height
- 27.9 in709 mm
- Section width
- 12.4 in315 mm
- Sidewall height
- 5.0 in126 mm
- Rim diameter
- 18 in457 mm
- Circumference
- 87.7 in2228 mm
- Revolutions per mile
- 722449 per km
- Inch size
- 27.9x12.4R18
Compare it with any other size in the tire size calculator.
Sizes you can swap to
These 18-inch sizes are within two width steps and 3% of a 315/40R18's overall height, the usual limit before the speedometer, ABS and transmission notice. The closest is 305/40R18, 1.1% shorter (0.31 in). Wider sizes also need room in the wheel well and a rim width that suits them.
Plus and minus sizes
Changing rim size means changing the sidewall to keep the same overall height. On 16-inch or 17-inch or 19-inch or 20-inch rims, these are the closest matches to a 315/40R18.
Other 18-inch sizes near 315/40R18
315 mm wide, other sidewalls
40 series, other widths
See the other sizes for this rim on 18-inch tire sizes.
Shop 315/40R18 tires
These open each store's own list of 315/40R18 tires, where you can filter by type, load and speed rating.
315/40R18 questions
How tall is a 315/40R18 tire?
About 27.9 inches (709 mm) from the ground to the top of the tread, unloaded. On the vehicle, carrying weight, it sits a little lower.
What does 315/40R18 mean?
315 is the section width in millimetres (12.4 in). 40 means the sidewall is 40% of that width: 126 mm, or 5.0 in. R means radial construction, and 18 is the rim diameter in inches.
Can I use 305/40R18 instead of 315/40R18?
305/40R18 is 1.1% shorter (0.31 in) and 10 mm narrower, which is inside the usual 3% rule. With it fitted, the speedometer shows 60 mph when you are doing 59.3 mph.
What is 315/40R18 in inches?
In inch terms it is 27.9x12.4R18: 27.9 inches tall, 12.4 inches wide, for an 18-inch rim.
How many revolutions per mile does a 315/40R18 make?
About 722 turns per mile, worked out from its unloaded circumference of 87.7 inches. Makers list slightly higher numbers for their own tires, because a loaded tire rolls on a smaller radius.