Rosetta: Unit Converter

Translate measurements instantly. Rosetta is a calm, ad-free unit converter for everyday checks — currency, weight, length, temperature, and ten more categories — with fast two-way input and no tracking.

A unit converter that respects your time and your data. Tap either side of the screen to make it the active value; the other side recomputes instantly. Both cards are first-class, so you can convert in either direction with a single tap. Star up to ten favorites for one-tap reuse from the home screen.

THIRTEEN CATEGORIES
• Currency — 165 ISO currencies, with live exchange rates sourced from the European Central Bank via the Frankfurter API
• Length — meters, feet, miles, kilometers, yards, inches, and more
• Mass / Weight — grams, kilograms, pounds, ounces, stones
• Temperature — Celsius, Fahrenheit, Kelvin
• Volume — liters, gallons, cups, fluid ounces, milliliters
• Speed — m/s, km/h, mph, knots
• Area — m², ft², acres, hectares
• Time — seconds, minutes, hours, days
• Energy — joules, calories, kilowatt-hours
• Power — watts, kilowatts, horsepower
• Pressure — pascals, psi, bar
• Data — bytes, kilobytes, megabytes, gigabytes (binary and decimal)
• Angle — degrees, radians, gradians

A MEASUREMENT CONVERTER THAT WORKS OFFLINE
Twelve of the thirteen categories work fully offline, with no network call required. Currency is fetched once from the Frankfurter API (sourced from the European Central Bank and 54 other central banks; no API key, no quota). After the first fetch, rates are cached on your device, so the currency converter keeps working offline. The "as of" date in the app tells you exactly how fresh the rates are.

WHY ROSETTA IS DIFFERENT
Most unit converters earn their keep by stuffing your screen with banner ads and asking you to upgrade. Rosetta does not.

• No ads — anywhere, ever
• No tracking — no analytics SDK ships in the app
• No accounts — there is nothing to sign up for
• No settings — the defaults are the right defaults
• No popups, no interstitials, no paywalls
• Works offline — the only network call is the optional currency rate refresh

DESIGNED TO STAY OUT OF YOUR WAY
• Two-way input — start with either side and the other recomputes
• Tap any result to copy. A quiet "Copied" toast confirms
• Star up to ten favorites; long-press a favorite to remove
• Light and dark mode automatic
• Locale-aware number formatting (1,234.5 vs 1.234,5)
• Gentle haptics on key actions
• Search across every unit in every category from the home screen

THE NAME
Rosetta is named after the Rosetta Stone — the artifact that made translation between systems possible. The app treats unit conversion as translation, not transformation. Kilograms and pounds are the same quantity in two languages.

FREE. NO IN-APP PURCHASES.
Rosetta is free, and free of the things that make most free apps unpleasant. There is no Pro tier, no subscription, no upsell. If you find this measurement converter useful, the best thanks is to tell someone who would also find it useful.

Made by Optiwise.
Support: contact@optiwise.us
Web: rosetta.optiwise.us