Tire Size Calculator
Calculate tire diameter, sidewall height, circumference, and revolutions per mile from a tire size code like 215/65R16.
How to use this calculator
👉 Fill in the boxes below and your answer appears instantly — no maths needed, we do it all for you! 🎉
In plain English — what does this do?
📊 A helper for daily life! Things like working out your age, how much to tip, what a sale price is, or how long until your birthday. Quick and easy answers for real life!
A tire size calculator converts standard tire size codes (like 215/65R16) into actual measurements: total diameter, sidewall height, circumference, and revolutions per mile. This helps when comparing tire sizes, calculating speedometer accuracy, or planning wheel upgrades.
Total Diameter
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Sidewall Height
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Circumference
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Rev / Mile
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What is Tire Size Calculator?
A tire size calculator converts standard tire size codes (like 215/65R16) into actual measurements: total diameter, sidewall height, circumference, and revolutions per mile. This helps when comparing tire sizes, calculating speedometer accuracy, or planning wheel upgrades.
How to use it
- 1️⃣ Either type the full tire code (e.g. 215/65R16) into the text field and click Parse, or
- 2️⃣ Enter the three values manually: section width in mm, aspect ratio %, and rim diameter in inches.
- 3️⃣ Click Calculate to see all tire dimensions.
- 4️⃣ Use revolutions per mile to check speedometer accuracy when switching tire sizes.
Formula
💡 See it in action — a real example
❓ Common questions
- What do the numbers in a tire code mean?
- 215/65R16 means: 215 = section width in mm, 65 = aspect ratio (sidewall height as % of width), R = radial construction, 16 = rim diameter in inches.
- How does tire size affect speedometer?
- A larger diameter tire covers more distance per revolution, making your actual speed higher than the speedometer reads. A smaller tire does the opposite.
- What is aspect ratio?
- Aspect ratio is the sidewall height as a percentage of the tire's section width. A 65 aspect ratio means the sidewall height is 65% of 215mm = 139.75mm.
- Can I put any tire size on my car?
- No. Tire size is limited by wheel well clearance, load rating, and speed rating. Always check the manufacturer's recommended tire size range.
- What is a plus-size tire upgrade?
- A plus-size upgrade uses a wider tire with a lower aspect ratio on a larger rim, keeping the overall diameter nearly the same to preserve speedometer accuracy.