Convrt: Unit Converter
A converter for 217 units across 23 categories, plus live currency and crypto rates — built to cut the number of taps it takes to reach the answer.
Free · No account · Unit conversion works offline
Problem
Other unit converters force a fixed order before you are allowed to type: pick a category, pick the source unit, pick the target unit, then enter a number. For a conversion done several times a day, that ritual takes longer than the arithmetic it wraps.
Solution
Built an Android converter that attacks the tap friction rather than the unit count: global unit search, categories you can pin to the top, a custom keypad that never covers the result and does the arithmetic itself, a list of every unit in a category converted at once, and a conversion history. Unit conversion runs fully offline — only currency and crypto rates need a connection.
Fewer taps to the answer
Every screen removes a step: search straight to a unit, a keypad of its own, and a whole category readable at once.
Swipe to see more screens →
What makes it quicker
Six design decisions, all answering one question: how many taps until the number appears?
Everything on one screen
The categories you reach for most sit at the top, pinned with a tap on the star.
Search, don't hunt
Type kg, km or kWh and land on the unit itself, without guessing its category first.
A calculator on the keypad
The keypad adds, subtracts, multiplies and divides. Type 250 × 3 and it is 750 that gets converted, with no second app.
Every unit at once
One value converts the whole category, so metre, foot and inch read side by side.
Currency and crypto
Rates and coin prices carry the time they were fetched, and say so plainly when the connection drops.
Conversion history
Every conversion saves itself, so the number worked out earlier is still there when it is needed again.
The numbers behind it
How much it covers, and what keeps it correct.
Units
217/ 23 categories
From length and mass through to torque and illuminance.
Domain tests
197JVM
Conversion logic tested away from Android, as a regression fence.
Live rates
30currencies
Plus 16 crypto coins, both stamped with a fetch time.
What leaves the device, and what doesn't
Convrt has no accounts and no server of its own.
- No account, no login. Open the app and start using it.
- Unit conversion works offline. All the unit data ships inside the app.
- The connection is used for two things: fetching currency and crypto rates, and loading ads.
- No analytics or crash-reporting SDK. There is no Firebase and no third-party tracker in the build.
- Ads are served by Google AdMob. As a third party, AdMob accesses the device's Advertising ID.
- A one-time purchase through Google Play. It removes the ads. Google handles the payment details; they never reach me.
Convrt is the first real app in my apps factory, and the reference for how features get built on top of the shared core modules: the design system, ads, preference storage and networking are all reused from the same modules the next app will use.
Its conversion logic sits in a pure domain layer with no Android dependencies, so it can be tested quickly on the JVM without an emulator. The biggest design tension was carrying technical categories like torque and illuminance without leaving everyday users lost. The way out was not burying them in a menu, but a user-type choice on first run that pins the categories that fit.
The app’s privacy policy lives on its own page.