GarageCalc What 225/55R16 means
225 is the section width in millimeters (8.9 in). 55 is the aspect ratio: the sidewall is 55 percent of the width, so 225 × 0.55 = 124 mm (4.9 in). R is radial construction, and 16 is the wheel diameter in inches (406 mm). Stack two sidewalls on the wheel and you get the overall diameter: 406 + 2 × 124 = 654 mm, or 25.7 in.
A full marking adds a load index and speed rating after the size, for example 225/55R16 91V. Those two codes set how much weight and speed the tire is certified for; look them up in the load index chart and the speed rating chart.
Plus and minus sizing from 225/55R16
Going up one wheel size, the closest match is 245/45R17 at -0.2% diameter with a 110 mm sidewall instead of 124 mm. Going down one size, 225/60R15 is -0.4% with a taller 135 mm sidewall for more comfort and pothole margin. Anything inside 3 percent keeps the speedometer, ABS and gearing effectively stock; the comparison calculator shows the full speedometer table for any pair.
Frequently asked questions
How tall is a 225/55R16 tire?
25.7 inches (654 mm) in overall diameter: the 16-inch wheel (406 mm) plus two 124 mm sidewalls. Real tires land within about 1 to 2 percent of that depending on brand, tread depth and pressure.
What is 225/55R16 in inches?
25.7 x 8.9 R16: 25.7 inches tall, 8.9 inches wide, on a 16-inch wheel. The sidewall is 4.9 inches and the circumference is 80.9 inches, so the tire turns 783 times per mile.
What tire sizes are equivalent to 225/55R16?
Within 3 percent of the same diameter on the same 16-inch wheel: 205/60R16 (-0.2%), 215/60R16 (+1.6%), 215/55R16 (-1.7%); on a 17-inch wheel: 245/45R17 (-0.2%), 225/50R17 (+0.4%); on a 15-inch wheel: 225/60R15 (-0.4%), 205/65R15 (-1.0%). The percentage is the diameter change, which is also your speedometer error.