Cog: Gear Ratio Calculator

Instant gear ratios, RPM, and torque — type tooth counts and results appear live. 24-gear reference catalog. No ads, fully offline.

Stop guessing gear ratios. Cog gives you the answer the moment you finish typing. Built for engineers, mechanics, and hobbyists who need fast, reliable drivetrain math — offline, always.

— KEY FEATURES —

• Live calculation — enter driving teeth, driven teeth, and input RPM; gear ratio, output RPM, and mechanical advantage update instantly as you type • Torque summary — see whether your setup produces a speed reduction (torque multiplied) or speed increase (torque divided) with the exact multiplier shown • 24-gear reference catalog — real-world specifications for spur, helical, bevel, planetary, and worm gears, each with a plain-English use case description • Filter and search — browse the gear catalog by type or search by name to find the exact gear you need • Named setups — save your most-used gear configurations with custom names and notes, then recall them with a tap • 6 built-in example setups — bike low/high gears, industrial 4:1 reducer, clock escapement, wind turbine gearbox, and 40:1 worm drive get you started immediately • Full offline — no internet connection required, no account, no ads, no tracking

Cog is the fastest way to go from tooth counts to a complete gear ratio calculation on iPhone.

— Cog Gear Calc PREMIUM —

Premium unlocks the full Cog experience: unlimited saved gear setups, the complete 24-gear reference catalog, torque and mechanical-advantage breakdowns, and a 100% offline, ad-free calculator with no tracking.

Subscription options: • Weekly — $9.99 / week • Yearly — $49.99 / year (includes a 3-day free trial)

Payment is charged to your Apple Account at confirmation of purchase. Subscriptions renew automatically unless turned off at least 24 hours before the end of the current period. Your account is charged for renewal within 24 hours prior to the end of the period. Manage or cancel anytime in your Apple Account settings.

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