Tire Size Calculator
Tire Diameter Formula: Dia = (Rim × 25.4) + (Width × Ratio × 0.02) mm
For a 205/55R16 tire: overall diameter is 24.9 inches (631.9 mm), sidewall height is 4.4 inches (112.8 mm), and circumference is 78.2 inches (1985.2 mm).
Tire 1 (Current / Stock)
Tire 2 (New / Compare)
Dimension Differences
Width Diff: -
Sidewall Diff: -
Diameter Diff: -
Circumference Diff: -
Speedometer Error: -
Speedometer reading: when traveling at 60 mph on Tire 1, you will actually be traveling at - mph on Tire 2.
Tire Comparison Matrix
| Dimension | Tire 1 | Tire 2 | Difference |
|---|---|---|---|
| Section Width | - | - | - |
| Sidewall Height | - | - | - |
| Overall Diameter | - | - | - |
| Circumference | - | - | - |
| Revs per Mile (km) | - | - | - |
Frequently Asked Questions
What does a tire size like 205/55R16 mean?
205 is the section width in millimeters. 55 is the aspect ratio, meaning the sidewall height is 55% of the width. 16 is the diameter of the wheel rim in inches.
How does changing tire size affect the speedometer?
If you install a tire with a larger overall diameter, it has a larger circumference and covers more distance per revolution. This makes your speedometer read slower than your actual speed.
How do you calculate overall tire diameter?
Overall Diameter = (Rim Diameter × 25.4) + 2 × (Width × Aspect Ratio / 100). To get the result in inches, divide the final value by 25.4.