Tire size is written as a code on the tire’s sidewall — width, aspect ratio, and wheel diameter — and choosing an alternate size that doesn’t closely match your original specification can throw off your speedometer accuracy and affect handling. This car tire size calculator helps you find your vehicle’s correct size and compare alternate sizes to see how much they’d change your tire’s overall diameter and ground clearance before you buy new tires.
Original Tire (OEM)
New Tire
Speedometer Impact Verification
65.0
Speedo Reads (mph)
65.0
Actual Speed (mph)
Safe: Within 3% variance limit
Fitment & Clearance Insights
Ride Height
No Change
Wheel Well Filling
No Change
Strut / Suspension
No Change
Dimensional Comparison (Inches & Metric)
| Specification | Original (OEM) | New Tire | Difference |
|---|---|---|---|
| Overall Diameter | 0 | 0 | 0 |
| Section Width | 0 | 0 | 0 |
| Sidewall Height | 0 | 0 | 0 |
| Circumference | 0 | 0 | 0 |
| Revs per Mile | 0 | 0 | 0 |
Getting tire size right also affects fuel economy and tire wear, so it’s worth pairing this with checking your correct tire pressure once new tires are installed. Both are relatively small maintenance details, but they add up as part of your overall car maintenance cost over time.