Dotori Roman Numerals
Converts between ordinary numbers and Roman numerals, in both directions, as you type. Tap either box to choose the side you are editing; the other one follows every key.
What it does
Both directions, live
Type 1990 and MCMXC appears; type MCMXC and 1990 appears. Whichever box you last edited is the one the other is derived from, so switching boxes never rewrites what you typed.
A keypad for each side
Digits on the Arabic side, the seven Roman letters on the other — laid out in value order, I V X / L C D / M. There is no system keyboard, so half the screen is never covered.
Past 3999, written the classical way
A bar over a group multiplies it by 1000, and a second bar multiplies it again, so 4000 is IV with one bar and 4,000,000 is IV with two. The app draws every bar itself rather than relying on a font, and covers 1 to 3,999,999,999.
Non-standard forms are read, not rejected
IIII, VV and IC all give a value, and the standard spelling is shown next to it. Clock faces really do use IIII, so refusing it would be unhelpful.
See how it breaks down
Open the breakdown and 1990 becomes M (1000) + CM (900) + XC (90). It updates as you type.
A help page that teaches
The seven symbols, the six subtractive pairs, the repetition limits, the overline rule, and exactly how this app reads non-standard input. Every example is tappable — press one and it loads into the converter.
Requirements
| Platform | Android (Kotlin, Jetpack Compose) |
|---|---|
| Package name | com.droidactor.roman |
| Minimum Android | Android 8.0 (API 26) |
| Target Android | API 36 |
| Range | 1 to 3,999,999,999 |
| Network | Not used for conversion — the app works offline |
| Permissions | Vibration only. No location, contacts, storage, camera or microphone |
| Price | Free, supported by ads (Google AdMob) |
| Accounts | None. No sign-in, no registration. |
| Status | Published on Google Play — store listing |
Known limits
The app starts at 1 — Roman numerals have no symbol for zero and no way to write a negative number or a fraction. There is no text selection or clipboard support yet. The overline is drawn rather than typed, so a screen reader states it in words instead: “I V with one bar, times one thousand, then X I I, value 4012”.
Privacy
Conversion happens entirely on your phone. Nothing you type is stored or sent anywhere — close the app and the numbers are gone. The only things kept are the three settings you choose: theme, display language and screen orientation.
Support
Bug reports, questions and feature requests go to droidactor@gmail.com.