Tire Size Calculator
Compare two tire sizes side by side with visual diagrams. See how a tire size change affects diameter, speedometer accuracy, ground clearance, and more.
Original Tire Size
New Tire Size
Popular Tire Size Comparisons
Click any comparison below to see the full visual analysis:
How to Read a Tire Size
A tire size like 225/65R17 means:
- 225 — Section width in millimeters (the width of the tire)
- 65 — Aspect ratio (sidewall height as a percentage of width)
- R — Radial construction (virtually all modern tires)
- 17 — Rim diameter in inches
Why Tire Size Matters
Changing tire size affects your speedometer accuracy, fuel economy, handling, ride comfort, and ground clearance. A larger diameter tire will make your speedometer read slower than actual speed, while a smaller diameter will make it read faster.
Rule of thumb: Stay within 3% of your original tire's overall diameter to avoid issues with ABS, traction control, and speedometer accuracy.
FAQ
Can I put a different size tire on my car?
Yes, but you should stay within 3% of your original tire's overall diameter. Larger deviations can affect speedometer accuracy, ABS, traction control, and may void your warranty.
Will bigger tires affect my speedometer?
Yes. Larger diameter tires make your speedometer read slower than your actual speed, while smaller tires make it read faster. Our calculator shows the exact speedometer error.
What does the aspect ratio mean?
The aspect ratio is the sidewall height expressed as a percentage of the tire width. A 205/55R16 has a sidewall height of 55% of 205mm = 112.75mm.
Can I change rim size without changing tire diameter?
Yes, this is called "plus sizing." You increase rim diameter while decreasing the aspect ratio to keep the overall diameter similar. For example, going from 205/55R16 to 215/45R17.