Speedometer Error Calculator
Find your true speed after a tire-diameter change. This free online automotive & vehicles calculator runs entirely in your browser — no signup, no data sent anywhere.
Inputs
Results
How It Works (Formula & Method)
The speedometer is calibrated for the original tire diameter. A larger tire travels farther per revolution, so your true speed is the indicated speed times the ratio of new to original diameter. The error is the percentage difference.
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 Tire Diameter (in): 25.9
- New Tire Diameter (in): 27.7
- Indicated Speed (mph): 60
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 Speedometer Error Calculator compute?
The Speedometer Error Calculator takes 3 input values and returns 2 results. Calculate your true speed and the speedometer error after changing tire diameter, from the original diameter, the new diameter, and the indicated speed.
Is my data sent to a server?
No. The Speedometer Error 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.