Quick start
- Enter width in millimeters.
- Enter aspect ratio as a percent.
- Enter wheel diameter in inches.
Best uses
These are the situations this tool is meant for. If your task is close to one of these, the examples and notes below can help you choose the right inputs.
- Decode a metric tire size.
- Compare tire diameter and circumference.
- Estimate revolutions per mile.
- Understand how aspect ratio changes sidewall height.
What this calculator is solving
The Tire Size Calculator explains a metric tire size such as 225/60R16. It estimates sidewall height, total diameter, circumference, and revolutions per mile.
You do not need to memorize the formula first. Start by matching each input label on the calculator to the number, date, unit, or setting you actually have.
The formula in plain language
In plain language: The calculator multiplies width by aspect ratio for sidewall height, converts millimeters to inches, then adds two sidewalls to wheel diameter. The examples on the page are there so you can compare your inputs with a filled-out calculation before copying the answer.
If that sounds abstract, use the example cards on the calculator page. They show a complete set of inputs and the kind of answer you should expect.
How to read the answer
Read the headline result first. Then look at the smaller supporting lines because they explain the parts behind the answer, such as totals, units, ranges, or formula steps.
- Diameter is the overall tire height estimate.
- Sidewall shows one sidewall height.
- Revs per mile helps compare rolling size changes.
Common mistakes to avoid
If the answer looks strange, the most likely cause is a small input mismatch: the wrong unit, date, weight, scale, mode, or policy assumption.
- Do not assume a size fits because the math looks close.
- Do not ignore load rating, rim width, clearance, and manufacturer guidance.
- Changing diameter can affect speedometer and safety systems.
Research and references
These references shaped the calculator assumptions, unit choices, or safety notes.
Examples from the calculator
Diameter and revs per mile
Sidewall and diameter estimate
Larger diameter estimate
FAQ in plain language
When should I use the Tire Size Calculator?
Use it when your task matches one of these common needs: Decode a metric tire size. Compare tire diameter and circumference. It works best when you already know the values, dates, units, or settings the page asks for.
What is the Tire Size Calculator doing with my inputs?
In plain language: The calculator multiplies width by aspect ratio for sidewall height, converts millimeters to inches, then adds two sidewalls to wheel diameter. The examples on the page are there so you can compare your inputs with a filled-out calculation before copying the answer.
What should I double-check before trusting the answer?
Tire changes can affect safety, fitment, load rating, speedometer readings, braking, and driver-assist systems. Follow manufacturer guidance. Also check that you used the right unit, date, scale, or mode because small input changes can change the result.
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Privacy and copying results
Recent answers stay visible only while you work in the current browser tab. They are not sent to a server.
Use Copy answer when you want to paste the expression and result into notes, homework, a message, or another document. Check the units and assumptions before copying.