225/50R18 tire size in inches

A 225/50R18 tire measures

26.9" tall × 8.9" wide

4.43" sidewall on a 18" wheel. 751 revolutions per mile.

225/50R18 means a tire 225 mm wide, with sidewalls 50% as tall as the tire is wide (113 mm), radial construction (R), for a 18 inch wheel.

26.9"18" rim4.4"8.9" wide
225/50R18: 26.9 inches tall, 8.9 inches wide, on a 18 inch rim, drawn to scale

225/50R18 specs

Overall diameter (height)26.86 inches (682 mm)
Section width8.86 inches (225 mm)
Sidewall height4.43 inches (113 mm)
Wheel (rim) diameter18 inches
Circumference84.4 inches (2,143 mm)
Revolutions per mile751
Revolutions per kilometer467
Approximate rim width6.5" to 8.0"
In inches (flotation style)26.9x8.9R18
Aspect ratio50%

Calculated from the size. Real tires differ by brand, model and tread depth, typically by a few tenths of an inch.

Sizes that can replace 225/50R18 on a 18" wheel

These 18" sizes are within 3% of 225/50R18's overall diameter, the range most tire shops treat as interchangeable.

SizeDiameterWidthDifferenceReal speed at 60
205/55R1826.88"8.07"+0.1%60.0 mphCompare
325/35R1826.96"12.80"+0.4%60.2 mphCompare
285/40R1826.98"11.22"+0.4%60.3 mphCompare
245/45R1826.68"9.65"−0.7%59.6 mphCompare
255/45R1827.04"10.04"+0.7%60.4 mphCompare
315/35R1826.68"12.40"−0.7%59.6 mphCompare
275/40R1826.66"10.83"−0.7%59.6 mphCompare
195/60R1827.21"7.68"+1.3%60.8 mphCompare
335/35R1827.23"13.19"+1.4%60.8 mphCompare
215/50R1826.46"8.46"−1.5%59.1 mphCompare
235/50R1827.25"9.25"+1.5%60.9 mphCompare
195/55R1826.44"7.68"−1.5%59.1 mphCompare

Same height on other wheel sizes (plus and minus sizing)

SizeWheelDiameterDifference
285/35R1919"26.85"0.0%Compare
215/70R1515"26.85"0.0%Compare
235/75R1313"26.88"+0.1%Compare
275/50R1616"26.83"−0.1%Compare
245/25R2222"26.82"−0.1%Compare
275/55R1515"26.91"+0.2%Compare
295/25R2121"26.81"−0.2%Compare
205/80R1414"26.91"+0.2%Compare
335/30R1919"26.91"+0.2%Compare
315/40R1717"26.92"+0.2%Compare
345/25R2020"26.79"−0.2%Compare
185/75R1616"26.93"+0.2%Compare

One size up or down

Compare 225/50R18 with another size

With 235/50R18 tires, when your speedometer says 60 mph you are really going

60.9 mph

235/50R18 is +0.39 inches (+1.5%) in overall diameter. That is within the 3% most shops and makers allow.

225/50R18235/50R18Difference%
Overall diameter26.86"27.25"+0.39"+1.5%
Section width8.86"9.25"+0.39"+4.4%
Sidewall height4.43"4.63"+0.20"+4.4%
Circumference84.38"85.61"+1.24"+1.5%
Revolutions per mile750.9740.1−10.8−1.4%

Questions

How tall is a 225/50R18 tire?
A 225/50R18 tire is 26.9 inches tall (682 mm), calculated from the size. It is 8.9 inches wide with 4.4 inches sidewalls. Real tires vary by a few tenths of an inch between brands and tread patterns.
What does 225/50R18 mean?
225/50R18 means a tire 225 mm wide, with sidewalls 50% as tall as the tire is wide (113 mm), radial construction (R), for a 18 inch wheel.
How many revolutions per mile does a 225/50R18 tire make?
About 751 revolutions per mile, based on a circumference of 84.4 inches. Under load the tire flattens slightly, so the maker's published figure is usually a little higher.
What rim width fits a 225/50R18 tire?
Roughly 6.5" to 8.0". Check the tire maker's approved rim range for the exact model before buying wheels.
Can I use 205/55R18 instead of 225/50R18?
205/55R18 is +0.02 inches (+0.1%) in overall diameter, so at an indicated 60 mph you would be doing 60.0 mph. Differences under 3% are usually fine, but check clearance, load index and your vehicle's placard.

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