Tire Size Comparison Calculator
Compare two tire sizes for diameter difference and speedometer error. This free online automotive & vehicles calculator runs entirely in your browser — no signup, no data sent anywhere.
Inputs
Results
How It Works (Formula & Method)
Overall tire diameter is the rim diameter plus twice the sidewall height, where sidewall = width × aspect ratio. The tool computes both diameters, their percentage difference, and what your speedometer reads at a true 60 mph after the change (an oversized tire makes the speedometer read low).
Worked Example
Below is a worked example using the calculator's default values. The same numbers are pre-filled in the form above so you can press Calculate and see the result without typing anything.
Inputs used:
- Original Width (mm): 225
- Original Aspect (%): 45
- Original Rim (in): 17
- New Width (mm): 245
- New Aspect (%): 40
- New Rim (in): 18
With these inputs, the calculator computes the metrics shown in the Results panel. Change any value and press Calculate again to see how the result responds — the live widget and the chart both update instantly.
Frequently Asked Questions
What does the Tire Size Comparison Calculator compute?
The Tire Size Comparison Calculator takes 6 input values and returns 4 results. Compare two tire sizes (width/aspect/rim) to see the difference in overall diameter and the resulting speedometer error.
Is my data sent to a server?
No. The Tire Size Comparison Calculator runs entirely in your browser using static JavaScript. Your inputs are never transmitted to CalculatorHive or any third party, and nothing is stored after you close the page.
Is this calculator free to use?
Yes. Every calculator on CalculatorHive is completely free. There is no signup, no paywall, and no usage limit. The site is supported by display advertising and affiliate partnerships, which are clearly labeled.
How accurate is the result?
The math is mathematically exact for the inputs you provide. Real-world accuracy depends on how accurately your inputs reflect the real situation — defaults are typical values, not guarantees.