Tire Size Calculator
Calculate tire dimensions, compare sizes, and see speedometer differences when changing tire sizes.
Tire Size Format
225/45R17
225
Width (mm)
45
Aspect ratio (%)
R17
Rim (in)
Overall Diameter
24.97"
634.24 mm
Section width
225 mm
Sidewall height
101.25 mm
Circumference
78.45 in
Revolutions per mile
808
Size Comparison
Speedometer difference
Actual speed vs displayed speed
+0.4%
Diameter diff
+0.09"
Width diff
+20 mm
Height diff
-11.5 mm
Reading Tire Sizes
Tire sizes like 225/45R17 indicate: 225mm width, 45% aspect ratio (sidewall height as % of width), R for radial construction, and 17 inch rim diameter.
Plus Sizing
Plus sizing means using larger wheels with lower profile tires to maintain overall diameter. +1 means 1 inch larger wheels. Maintain overall diameter within 3% of original.
Effects of Size Changes
Larger tires increase ground clearance and speedometer error. Wider tires improve grip but may affect fuel economy. Keep overall diameter close to original to avoid transmission issues.