Tire Size Calculator
Calculate tire dimensions and compare sizes to check fitment and speedometer accuracy.
Stock Tire Size
New Tire Size (Optional)
Understanding Tire Sizes
Tire size is typically represented by a series of numbers and letters on the sidewall of the tire. For example, in the size "P215/65R15":
- P indicates the tire is for passenger vehicles
- 215 is the tire width in millimeters
- 65 is the aspect ratio (sidewall height as percentage of width)
- R indicates radial construction
- 15 is the rim diameter in inches
Use our tire size calculator above to compare different tire sizes and see how they affect your vehicle's performance and speedometer accuracy.
Why Tire Size Matters
Choosing the right tire size is crucial for several reasons:
- Safety: Incorrect tire sizes can affect handling, braking, and stability
- Speedometer Accuracy: Changing tire diameter affects speedometer readings
- Clearance: Larger tires may rub against wheel wells or suspension components
- Performance: Tire size affects acceleration, fuel economy, and ride comfort
How to Use the Tire Size Calculator
- Enter your current tire size in the "Stock Tire Size" section
- Enter the new tire size you're considering in the "New Tire Size" section
- Click "Calculate Tire Sizes" to see the comparison
- Review the results to understand the differences in diameter, width, and other parameters
Frequently Asked Questions
Can I put larger tires on my vehicle?
You can often go up or down one size from your original equipment tires without issues, but significant changes may require modifications and could affect your vehicle's warranty. Always consult with a tire professional before making major changes.
How much does tire size affect speedometer reading?
A 1-inch increase in overall tire diameter will typically cause your speedometer to read about 1-2 mph slower than your actual speed at highway velocities. Our calculator shows the exact percentage difference.
Will larger tires improve fuel economy?
Generally, larger, heavier tires decrease fuel economy due to increased rolling resistance and weight. However, some drivers choose taller tires to effectively lower engine RPM at highway speeds, which might improve fuel economy in some cases.
How do I know what tire sizes fit my vehicle?
Check your vehicle's owner's manual, the tire information placard (usually located on the driver's door jamb), or consult with a tire professional. Our calculator helps you compare sizes to ensure proper fitment.