Tire Size Calculator +

Compare & Speedo Error

Only for iPhone

Free · Designed for iPhone. Not verified for macOS.

iPhone

Pick 225/45R17 or 31x10.50R15 from a full list, then read diameter and how far the speedo will lie. ▶ Compare two tire sizes at a glance. Enter both specs and see the difference in diameter, circumference, sidewall and ride height, with a to-scale overlay so the size change is obvious. ▶ Check your speedometer. See how a new tire shifts your real speed versus the reading, plus an odometer-error percentage — the numbers that matter after an upsize. ▶ Find plus sizes. Enter a target and get alternate sizes within a few percent of the original diameter, grouped by rim so you can plan a clean plus-one or plus-two. ▶ Decode the markings. Load-index and speed-rating tables turn the numbers on the sidewall into kg and km/h, with P, LT and XL explained. ▶ Save your vehicles and share a result card. Works offline, no account needed. Results are for reference only. Fitment and clearance depend on your vehicle — always confirm with your owner's manual or a tire professional.

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Tap the size chip and a three-column sheet opens already on 225 / 45 / 17 — you are not stuck on 135 anymore. Flip Metric to Flotation on that same sheet and 31x10.50R15 sits next to a P-metric size, so diameter and speedo error are visible before you buy.

Version 1.2.1

The developer, heekyung moon, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .

  • Data Used to Track You

    The following data may be used to track you across apps and websites owned by other companies:

    • Identifiers
    • Usage Data

  • Data Not Linked to You

    The following data may be collected but it is not linked to your identity:

    • Identifiers
    • Usage Data
    • Diagnostics

Privacy practices may vary, for example, based on the features you use or your age. Learn More

Accessibility

The developer has not yet indicated which accessibility features this app supports. Learn More

Information

Seller
  • heekyung moon
Size
  • 54.1 MB
Category
  • Utilities
Compatibility
Requires iOS 16.4 or later.
  • iPhone
    Requires iOS 16.4 or later.
  • Mac
    Requires macOS 12.0 or later and a Mac with Apple M1 chip or later.
  • Apple Vision
    Requires visionOS 1.0 or later.
Languages
  • English
Age Rating
18+
Copyright
  • © 2026 Moon
  • Developer Website
  • Privacy Policy

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