225/45R18 tire size

A 225/45R18 tire is 26.0 inches (660 mm) tall and 8.9 inches (225 mm) wide, and fits a 18-inch wheel. In inch sizing it is about a 26.0x8.9R18.

Overall diameter25.97in660 mm

Drawn to scale from the nominal size.

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Size	Diameter	Difference	Width	Sidewall	Wheel
215/65R15	26.0″	+0.1%	8.5″	5.5″	15″
255/35R19	26.0″	+0.2%	10.0″	3.5″	19″
255/40R18	26.0″	+0.2%	10.0″	4.0″	18″
205/55R17	25.9″	−0.4%	8.1″	4.4″	17″
225/40R19	26.1″	+0.4%	8.9″	3.5″	19″
225/50R17	25.9″	−0.4%	8.9″	4.4″	17″
205/75R14	26.1″	+0.5%	8.1″	6.1″	14″
215/60R16	26.2″	+0.7%	8.5″	5.1″	16″
245/35R19	25.8″	−0.8%	9.6″	3.4″	19″
225/35R20	26.2″	+0.9%	8.9″	3.1″	20″
225/55R16	25.7″	−0.9%	8.9″	4.9″	16″
245/40R18	25.7″	−1.0%	9.6″	3.9″	18″

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

225: Section width: 225 mm (8.9 in) from sidewall to sidewall.
45: Aspect ratio: the sidewall is 45% as tall as the tire is wide, 101 mm (4.0 in).
R: Radial construction, used by almost every modern tire.
18: Fits a 18-inch wheel.

225/45R18 is about 26.0 inches tall and 8.9 inches wide, on a 18-inch wheel, roughly a 26.0x8.9R18 in inch sizing.

Yes. At 26.0 inches it is sold and fitted as a 26-inch tire.

215/65R15, 255/35R19, 255/40R18 are the closest common sizes, all within 0.2% of its diameter, so the speedometer stays close to accurate.

245/45R18 is 2.7% taller, so at an indicated 60 mph you would really be doing 61.6 mph. Compare 225/45R18 and 245/45R18.

About 777 per mile (483 per km), from a 81.6-inch circumference.