How to Use the Tire Size Comparison Tool
Tires aren't always labeled the same way, and not every size swap is straightforward. Enter two sizes above, and the tool shows you the difference in overall diameter, width, and sidewall height, along with the percentage of whether a size fits your vehicle.
What the Comparison Shows
Each size breaks down into three dimensions that affect fit and performance:
- Overall diameter: How tall the tire is when mounted. This affects ground clearance, how the vehicle sits, and your speedometer accuracy.
- Section width: How wide the tire is from sidewall to sidewall. Width affects how the tire fills the wheel well and how it performs in different road conditions.
- Sidewall height: The distance from the wheel rim to the outer edge of the tire. Taller sidewalls absorb more road impact. Shorter sidewalls respond more precisely to steering inputs.
You'll also see the percentage difference between the two sizes in overall diameter. That number matters for fitment. A change of more than 3% can affect how your vehicle reads speed and how the drivetrain behaves, particularly on all-wheel-drive and four-wheel-drive vehicles where tire sizes need to stay closely matched.
Common Reasons to Compare Tire Sizes
Having the exact dimensions in front of you changes how you shop. Some common situations where this helps:
- You want to go up a tire size for more clearance or a different look, and need to know the new tire will fit without rubbing.
- You're replacing one or two tires and want to confirm the new size matches what's already on the vehicle.
- You're comparing tires across brands, and the sizes are labeled differently.
- You're considering a different aspect ratio and want to know how that affects overall height.
- You're moving to a larger or smaller wheel diameter and need to know what tire size maintains the same overall diameter.
Understanding the Diameter Difference
Overall diameter is the dimension that matters most for clearance and speedometer accuracy. If a new tire is taller than your current size, your speedometer will read slightly low, because each wheel rotation covers more ground. Most vehicles tolerate a small difference without issues, but larger gaps can interfere with traction control systems and, on some all-wheel-drive vehicles, cause drivetrain wear over time.
The percentage difference shown in the comparison tells you where you stand. Under 3% from your original size is generally a safe swap for most passenger vehicles and light trucks. Over 3% is worth confirming with your vehicle's documentation or a mechanic before purchasing.
Before You Buy
Once you've identified a size you want, verify it's compatible with your wheel. Tire and wheel width need to fall within a compatible range, not just close. Most tire manufacturers publish fitment charts that list the compatible wheel widths for each tire size.
Only Tires carries a wide selection in both the size you have now and the size you're considering. After using this comparison tool, you can search directly on the site by size to see what's available across brands, tread type, and price points.
If one of your sizes is in metric format and the other is in inches, use the Metric to Standard Tire Conversion calculator to convert both to the same format before comparing.
