Tire Size Box

Tire size calculator

Type any tire size to see how tall and wide it really is, in inches and millimeters.

A 225/65R17 tire is

28.5" tall × 8.9" wide

Sidewall 5.76 inches, circumference 89.6 inches, 707 revolutions per mile. Fits rims about 6.0" to 7.5" wide.

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Thinking about a different size? See how much taller or wider it is and what your speedometer will really read.

With 235/65R17 tires, when your speedometer says 60 mph you are really going

61.1 mph

235/65R17 is +0.51 inches (+1.8%) in overall diameter. That is within the 3% most shops and makers allow.

225/65R17235/65R17Difference%
Overall diameter28.52"29.03"+0.51"+1.8%
Section width8.86"9.25"+0.39"+4.4%
Sidewall height5.76"6.01"+0.26"+4.4%
Circumference89.58"91.19"+1.61"+1.8%
Revolutions per mile707.3694.8−12.5−1.8%

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Questions

How do I convert a tire size to inches?
Multiply the width (first number, in mm) by the aspect ratio (second number, as a percent) to get the sidewall height in mm. Double it, divide by 25.4 and add the wheel diameter. For 225/65R17: 225 × 0.65 = 146.25 mm, × 2 = 292.5 mm = 11.5 inches, + 17 = 28.5 inches tall.
How much bigger can I go on tire size?
Most tire shops and vehicle makers recommend staying within 3% of the original overall diameter. Beyond that, the speedometer, ABS and stability control can be affected, and the tire may rub.
Does a bigger tire change my speedometer?
Yes. A taller tire covers more ground per turn, so you go faster than the speedometer shows. A tire 3% taller means 61.8 mph when the speedometer says 60.
What is the difference between metric and flotation sizes?
Metric sizes like 285/75R16 give width in millimeters and sidewall as a percentage. Flotation sizes like 33x12.50R15 give the overall diameter and width in inches directly. Both end with the wheel diameter.

Also see: how to read a tire size, load index chart, speed ratings and how old is my tire.