225/45R17 Tire Size Calculator & Comparison
Parse metric (225/45R17) or flotation (33x12.5R15) tire codes, get sidewall height, overall diameter, circumference and revolutions per mile/km, and compare two sizes with the resulting speedometer error.
Result
This page opens the tire size calculator with 225/45R17 already entered as the current tire — a very common size on mid-size sedans and hot hatches. Its sidewall height works out to 225 mm × 45% ≈ 101 mm, giving an overall diameter of about 634 mm (24.97 in) and a circumference of roughly 1,993 mm (78.5 in), which comes to about 807 revolutions per mile or 502 per kilometer.
Enter the size you are considering — a plus-size 235/45R17, a different aspect ratio like 225/40R18, or even a flotation truck size — in the second field, and the calculator instantly shows the diameter gap in millimeters, inches and percent, side by side with a to-scale diagram of both tires and rims.
The comparison also covers the practical consequence of that gap: a taller replacement tire makes your speedometer read slower than your real speed, a shorter one makes it read faster. The exact percentage is computed from the diameter ratio, not a rule of thumb, so you know precisely what to expect before you buy.