Tire Size Calculator Compare sizes visually, find alternatives, check speedometer error
Pro Tire Size Calculator
Advanced comparison with scenario analysis, performance impact, and detailed specifications
Specifications Comparison
Performance Impact
Speedometer Correction
| Speedometer | Actual Speed | Difference | Odometer at 10,000 mi |
|---|---|---|---|
| 30 mph | 29.1 mph | -0.9 mph | 10293 mi shown |
| 40 mph | 38.8 mph | -1.2 mph | 10293 mi shown |
| 50 mph | 48.5 mph | -1.5 mph | 10293 mi shown |
| 60 mph | 58.2 mph | -1.8 mph | 10293 mi shown |
| 70 mph | 68 mph | -2 mph | 10293 mi shown |
| 80 mph | 77.7 mph | -2.3 mph | 10293 mi shown |
| 90 mph | 87.4 mph | -2.6 mph | 10293 mi shown |
| 100 mph | 97.1 mph | -2.9 mph | 10293 mi shown |
Close Alternatives to 225/65R17
How to Use This Calculator
This tire size calculator has three modes to help you with different tasks:
Compare Two Sizes
Select your original tire size and the new size you're considering. The calculator instantly shows the difference in overall diameter, width, sidewall height, circumference, and revolutions per mile. The visual overlay shows both tires side-by-side so you can see the size difference at a glance. A green badge means the swap is safe (under 3% diameter difference), yellow means caution, and red means not recommended.
Find Alternatives
Enter your current tire size and the calculator finds all compatible sizes within a safe diameter range. Results are sorted by how close they are to your original size. Click any alternative to instantly compare it in the Compare tab.
Speedometer Error
When you change tire size, your speedometer becomes inaccurate because it's calibrated for the original tire's circumference. Enter both sizes and this tab shows a complete speed correction table — at every common speed, you'll see what your speedometer says vs. your actual speed.
Tire Size Formula
Circumference (mm) = π × Overall Diameter
Revolutions per Mile = 1,609,344 ÷ Circumference
Speedometer Error (%) = (New Diameter − Old Diameter) ÷ Old Diameter × 100
Ground Clearance Change (mm) = (New Diameter − Old Diameter) ÷ 2
Example
Mike's RAV4 came with 225/65R17 tires (overall diameter: 724.3mm). He wants to upgrade to 18-inch wheels with 235/60R18 tires (overall diameter: 739.1mm). The calculator shows a +2.0% diameter increase — well within the safe zone. His ground clearance increases by 7.4mm, and at 60 mph his speedometer will read about 58.8 mph (actual). Mike also sees that 225/60R18 is a closer match at only +0.5% difference if he prefers minimal speedometer impact.