215/35R18 in inches

A 215/35R18 tire is 23.9″ tall and 8.5″ wide, and fits a 18″ wheel. In inches it is written 23.9×8.5R18.

Diameter23.93″

Width8.46″

Sidewall2.96″

Drawn to scale. Nominal dimensions calculated from the size code.

Manufacturer data

How tall 215/35R18 tires really are

Heights published by Michelin for the one tire in this size. Their published revolutions per mile work out to 23.2″ under load (below).

The one tire listed, the Michelin Pilot Sport 4 S, measures 23.90″: 0.03″ shorter than the size code's 23.93″.

Height under load23.2″

Published revs per mile (870) mean the tire rolls like a 23.2″ tire on the vehicle. Use this for speedometer calibration.

1 tire in 215/35R18

Sort by the spec you care about.

	Load					Revs/mi	Source
Michelin Pilot Sport 4 SPerformance	XL · 84(Y)	23.90	18.6	9.5	1,102	870	Spec page

Is 215/35R18 a 24-inch tire?

≈24″

Yes. The size code works out to 23.93″, and the 1 tire here publishes 23.90″, so people call it a 24.

Compare with nearby sizes

Differences in overall diameter, calculated from each size code.

Size	Diameter ″	vs 215/35R18	Difference
245/35R17	23.75	-0.17″	-0.7%
215/40R17	23.77	-0.15″	-0.6%
195/45R17	23.91	-0.02″	-0.1%
205/45R17	24.26	+0.34″	+1.4%
205/40R18	24.46	+0.53″	+2.2%
285/30R18	24.73	+0.81″	+3.4%
245/35R18	24.75	+0.83″	+3.5%
215/40R18	24.77	+0.85″	+3.5%
295/30R18	24.97	+1.04″	+4.4%
255/35R18	25.03	+1.10″	+4.6%

How to read 215/35R18

How to read any tire size

How 215/35R18 84Y is printed on the sidewall. It's the most common code among the 1 tire here; tires in this size come in other load and speed ratings too.

1215Section width

215 mm across the widest point, or 8.46 inches. Every 215 size

235Aspect ratio

A percentage, not a measurement: the sidewall is 35% as tall as the tire is wide, which is 75.3 mm or 2.96 inches.

3RConstruction

Radial construction.

418Wheel diameter

Mounts on a 18-inch wheel. Approved wheel widths run 7.0″ to 8.5″.

584Load index

Each tire carries up to 1,102 lb (500 kg) at its maximum pressure.

6YSpeed rating

Rated for up to 186 mph sustained.

XLExtra load

Printed after the size.

Specification	Inches	Metric
Overall diameter	23.93	608 mm
Section width	8.46	215 mm
Sidewall height	2.96	75.3 mm
Circumference	75.2	1,909 mm
Revolutions per mile (calculated, unloaded)	843.0	524 per km
Revolutions per mile (published by manufacturers)	870	541 per km
Approved wheel width	7.0–8.5	178–216 mm

Speedometer error after switching to 215/35R18

Your actual speed– mph

Questions about 215/35R18

What is 215/35R18 in inches?

23.93 inches tall, 8.46 inches wide, on a 18-inch wheel. Written in inches, that is roughly 23.9×8.5R18.

What wheel width do I need for 215/35R18?

Manufacturers approve 7.0–8.5″ wide wheels for this size.

How many revolutions per mile does a 215/35R18 make?

Published figures run 870 revolutions per mile. The calculated figure is 843.0, but manufacturers measure the tire under load, where it rolls on a smaller radius.