235/45R18 tire size

A 235/45R18 tire is 26.3 inches (669 mm) tall and 9.3 inches (235 mm) wide, and fits a 18-inch wheel. In inch sizing it is about a 26.3x9.3R18.

Overall diameter26.33in669 mm

Drawn to scale from the nominal size.

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Size	Diameter	Difference	Width	Sidewall	Wheel
215/55R17	26.3″	−0.1%	8.5″	4.7″	17″
205/70R15	26.3″	−0.1%	8.1″	5.6″	15″
235/40R19	26.4″	+0.3%	9.3″	3.7″	19″
225/35R20	26.2″	−0.5%	8.9″	3.1″	20″
235/35R20	26.5″	+0.6%	9.3″	3.2″	20″
205/65R16	26.5″	+0.6%	8.1″	5.2″	16″
215/60R16	26.2″	−0.6%	8.5″	5.1″	16″
205/75R14	26.1″	−0.8%	8.1″	6.1″	14″
225/40R19	26.1″	−0.9%	8.9″	3.5″	19″
275/35R19	26.6″	+1.0%	10.8″	3.8″	19″
255/40R18	26.0″	−1.1%	10.0″	4.0″	18″
255/35R19	26.0″	−1.1%	10.0″	3.5″	19″

Within 3% of the original diameter is the range most tire shops treat as a direct swap. Check load index and clearance too.

235: Section width: 235 mm (9.3 in) from sidewall to sidewall.
45: Aspect ratio: the sidewall is 45% as tall as the tire is wide, 106 mm (4.2 in).
R: Radial construction, used by almost every modern tire.
18: Fits a 18-inch wheel.

235/45R18 is about 26.3 inches tall and 9.3 inches wide, on a 18-inch wheel, roughly a 26.3x9.3R18 in inch sizing.

Nearly. It measures 26.3 inches, so it falls between 26 and 27 inches.

215/55R17, 205/70R15, 235/40R19 are the closest common sizes, all within 0.3% of its diameter, so the speedometer stays close to accurate.

235/50R18 is 3.5% taller, so at an indicated 60 mph you would really be doing 62.1 mph. Compare 235/45R18 and 235/50R18.

About 766 per mile (476 per km), from a 82.7-inch circumference.