225/55R20 tire size in inches

A 225/55R20 tire measures

29.7" tall × 8.9" wide

4.87" sidewall on a 20" wheel. 678 revolutions per mile.

225/55R20 means a tire 225 mm wide, with sidewalls 55% as tall as the tire is wide (124 mm), radial construction (R), for a 20 inch wheel.

29.7"20" rim4.9"8.9" wide
225/55R20: 29.7 inches tall, 8.9 inches wide, on a 20 inch rim, drawn to scale

225/55R20 specs

Overall diameter (height)29.74 inches (756 mm)
Section width8.86 inches (225 mm)
Sidewall height4.87 inches (124 mm)
Wheel (rim) diameter20 inches
Circumference93.4 inches (2,373 mm)
Revolutions per mile678
Revolutions per kilometer421
Approximate rim width6.5" to 8.0"
In inches (flotation style)29.7x8.9R20
Aspect ratio55%

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 225/55R20 on a 20" wheel

These 20" sizes are within 3% of 225/55R20's overall diameter, the range most tire shops treat as interchangeable.

SizeDiameterWidthDifferenceReal speed at 60
275/45R2029.74"10.83"0.0%60.0 mphCompare
355/35R2029.78"13.98"+0.1%60.1 mphCompare
245/50R2029.65"9.65"−0.3%59.8 mphCompare
305/40R2029.61"12.01"−0.5%59.7 mphCompare
315/40R2029.92"12.40"+0.6%60.4 mphCompare
345/35R2029.51"13.58"−0.8%59.5 mphCompare
255/50R2030.04"10.04"+1.0%60.6 mphCompare
285/45R2030.10"11.22"+1.2%60.7 mphCompare
265/45R2029.39"10.43"−1.2%59.3 mphCompare
215/60R2030.16"8.46"+1.4%60.8 mphCompare
215/55R2029.31"8.46"−1.5%59.1 mphCompare
235/55R2030.18"9.25"+1.5%60.9 mphCompare

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

SizeWheelDiameterDifference
235/85R1414"29.73"−0.1%Compare
205/85R1616"29.72"−0.1%Compare
245/40R2222"29.72"−0.1%Compare
295/55R1717"29.78"+0.1%Compare
215/75R1717"29.70"−0.2%Compare
235/80R1515"29.80"+0.2%Compare
245/45R2121"29.68"−0.2%Compare
295/25R2424"29.81"+0.2%Compare
305/45R1919"29.81"+0.2%Compare
315/35R2121"29.68"−0.2%Compare
325/30R2222"29.68"−0.2%Compare
275/50R1919"29.83"+0.3%Compare

One size up or down

Compare 225/55R20 with another size

With 235/55R20 tires, when your speedometer says 60 mph you are really going

60.9 mph

235/55R20 is +0.43 inches (+1.5%) in overall diameter. That is within the 3% most shops and makers allow.

225/55R20235/55R20Difference%
Overall diameter29.74"30.18"+0.43"+1.5%
Section width8.86"9.25"+0.39"+4.4%
Sidewall height4.87"5.09"+0.22"+4.4%
Circumference93.44"94.80"+1.36"+1.5%
Revolutions per mile678.1668.3−9.7−1.4%

Questions

How tall is a 225/55R20 tire?
A 225/55R20 tire is 29.7 inches tall (756 mm), calculated from the size. It is 8.9 inches wide with 4.9 inches sidewalls. Real tires vary by a few tenths of an inch between brands and tread patterns.
What does 225/55R20 mean?
225/55R20 means a tire 225 mm wide, with sidewalls 55% as tall as the tire is wide (124 mm), radial construction (R), for a 20 inch wheel.
How many revolutions per mile does a 225/55R20 tire make?
About 678 revolutions per mile, based on a circumference of 93.4 inches. Under load the tire flattens slightly, so the maker's published figure is usually a little higher.
What rim width fits a 225/55R20 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 275/45R20 instead of 225/55R20?
275/45R20 is 0.00 inches (0.0%) 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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