Gear Ratio Calculator

1. Provider and app license

Gear Ratio Calculator is provided under the Set In Stone brand by the app provider identified on its App Store listing. Contact [email protected] with “Gear Ratio Calculator” in the subject. Apple’s Standard End User License Agreement governs the app license. These additional terms describe the utility, local data, and purchases; they do not replace Apple’s license or limit mandatory consumer rights.

2. Calculations and practical limits

The app calculates reduction ratios, input and output RPM, theoretical road speed, required RPM, final drive, gearing comparisons, percentage changes, and numerical tooth-pair matches. Results depend on the values and units you enter and the formulas’ assumptions.

Road-speed calculations assume ideal gearing, the entered outer tire size, and no tire slip. They do not account for load, deformation, traction, drag, available power, or achievable top speed. Reverse tooth combinations are numerical matches, not guarantees of fit, chain length, tooth profile, strength, clearance, or mechanical compatibility.

Verify consequential gearing changes independently against manufacturer specifications and appropriate mechanical advice. Do not operate the app while driving or use its results as a certification of vehicle safety or roadworthiness.

3. Free tools and Lifetime Pro

The app is a free download. Basic tooth-count gear ratio and input/output RPM calculations are free. The optional Lifetime Pro unlock adds road speed and required RPM, final drive, comparisons, percentage changes, reverse tooth solving, saved setups, and history.

Lifetime Pro is a single non-consumable purchase billed once to your Apple Account after confirmation. It has no weekly, monthly, annual, recurring, or trial plan. The purchase confirmation shows the actual localized price and applicable taxes before payment. The intended US base price is $6.99; storefront prices may differ.

Lifetime refers to the purchased non-consumable app entitlement. It does not guarantee indefinite device compatibility, uninterrupted operation, or perpetual availability of Apple services. These terms do not retroactively remove purchased rights or alter a completed purchase contrary to law.

4. Restore, payment issues, and refunds

Use Restore Purchases in Settings or the Pro sheet with the Apple Account used for purchase. StoreKit verifies eligible access. Pending, failed, canceled, unverified, refunded, or revoked purchases may not grant access. Purchase and restoration may need an internet connection.

Apple manages payment methods, billing, and App Store refund requests. Contact Apple billing support for a payment or refund issue and our support email for app behavior. Removing the app or clearing its data does not cancel or refund the one-time purchase. Nothing here excludes remedies or refund rights required by law.

5. Your saved information

You are responsible for the inputs, unit selections, and setup names you enter and for maintaining suitable device backups. Your local entries are not uploaded to a Set In Stone server. Deleting a setup, clearing history, or removing app storage may permanently remove it.

History is a convenience limited to the most recent 20 entries, not a complete audit record. Restore Purchases restores paid access and cannot recover deleted local records.

6. Availability and responsibility

The app depends on compatible Apple devices, operating-system functionality, and Apple purchase services. Software defects, interruptions, and third-party outages may affect results or availability. We do not guarantee error-free calculations or fitness for every mechanical task.

The app is provided subject to Apple’s Standard EULA and applicable law. Any limitations apply only to the extent legally permitted; these terms do not exclude liability or remedies that cannot lawfully be excluded, including mandatory consumer rights.

7. Privacy and changes

Information processing is described at https://setinst.one/apps/gearratiocalculator/privacy/. Apple and linked services operate under their own applicable terms and notices.

These terms are effective October 9, 2026. Material changes will be published with a revised date and additional notice where required. Contact [email protected] for support or questions.