How tall is a 225/55R18 tire?

A 225/55R18 has a nominal overall diameter of 27.74 inches (705 mm), calculated as the 18-inch wheel plus two sidewalls. This is the unloaded figure — a fitted tire sits fractionally shorter under the weight of the vehicle.

What wheel size does a 225/55R18 tire fit?

A 225/55R18 fits a wheel of 18 inches in diameter. The wheel also has to be within the rim width range the manufacturer publishes for this size, which is printed in the tire's spec sheet.

What do the numbers in 225/55R18 mean?

225 is the section width in millimetres. 55 is the aspect ratio — the sidewall is 55% of the width, so 123.8 mm here. R marks the construction (radial). 18 is the wheel diameter in inches.

Size Dimensions & Specs

Tires Size 225/55R18

Dimensions, specs, and every size 225/55R18 tire currently in stock

Overall Height

27.74"

705 mm · calculated

Section Width

225 mm

8.86 inches

Sidewall Height

4.87"

123.8 mm · 55% profile

Wheel Diameter

18"

457.2 mm

225/55R18 Specifications

Read directly from the size code. Load index, speed rating, and rim width range vary by model.

Specification	Imperial	Metric
Section width	8.86 in	225 mm
Aspect ratio	55%	—
Sidewall height	4.87 in	123.8 mm
Overall diameter (calculated)	27.74 in	705 mm
Wheel / rim diameter	18 in	457.2 mm
Construction	Radial	—

What does 225/55R18 mean?

Reading the code on your sidewall

Section width

225 mm

The distance from sidewall to sidewall across the tire's widest point.

Aspect ratio

55% profile

The sidewall stands 55% of the section width, which is 123.8 mm on this size.

Construction (R)

Radial

The body plies run across the tire at right angles to the direction of travel.

Wheel diameter

18 in

Fits a wheel measuring 18 inches across.

225/55R18 Questions & Answers

Dimensions and fitment guidelines for size 225/55R18

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