Roman Read

XLIX is 49, XCIV is 94, and both of them turn on one rule that everything else in Roman numerals is built out of: a smaller letter written in front of a bigger one is taken away from it, and anywhere else it is added on. Roman Read gives you eight conversions in a round, four each way, and four answers to choose from. Every wrong answer on the board is a real mistake with a name — the pair written out the long way, the pair the wrong way round, the small letter dropped or stacked, the same pair one rung too high — so picking one tells you which rule you just broke instead of telling you nothing.

It runs entirely on your device: 0 network requests, works offline. No ads, no account, nothing to buy, and no betting, money or prizes of any kind.

1. Focus the board — click it, or press Tab until it is focused.
2. Read the prompt. A number means write it as a numeral; a numeral means read it as a number. The round alternates, four of each, so you never settle into one direction.
3. Move between the four answers with the up and down arrows. Left and right do the same thing, and the list wraps at both ends.
4. Press Enter to commit the answer under the cursor. A right answer moves you on; a wrong one rules that option out with a ✕, strikes it through, and spends one move.
5. Read the line underneath. After every answer it names the rule involved — why the numeral breaks down the way it does, or exactly what the option you picked would really read as.
6. Watch the moves. You get eight plus a few spare, and the spares are the only wrong answers the round has room for. Picking an option that is already ruled out costs nothing.

How do you read a Roman numeral like XLIX?

Left to right, one group at a time, and only ever take a letter away when the letter immediately after it is bigger. XLIX breaks into XL and IX: in XL the X (10) sits in front of the L (50), so it is 50 − 10 = 40; in IX the I (1) sits in front of the X (10), so it is 10 − 1 = 9. Add the groups: 40 + 9 = 49. The trap is reading the letters one at a time and adding all four — that gives 10 + 50 + 1 + 10 = 71, which is the single most common misreading there is. There are only six subtractive pairs in the whole system — IV 4, IX 9, XL 40, XC 90, CD 400, CM 900 — so once you can spot those six on sight, every numeral is just those groups plus plain letters added together.

Why is 49 not written IL?

Because only I, X and C are allowed to subtract, and each of them only from the next two symbols up: I from V and X, X from L and C, C from D and M. IL would need I to be taken from L, which is four rungs away, so it is not a numeral at all even though you can guess what it means. The same rule kills IC for 99 and VL for 45 — V, L and D never subtract from anything. Written properly, 49 is XL + IX and 99 is XC + IX.

Why does the game show me both directions in one round?

Because reading and writing a numeral are genuinely different jobs. Reading is a comparison — look at each letter, check the one after it, add or subtract. Writing is a subtraction down a ladder — take the biggest value you can, write its letters, and repeat with what is left. Drill one of them on its own and you get quick at that one while the other stays slow. The round is dealt four and four and then shuffled, so the split is guaranteed rather than left to chance.

Are the wrong answers just random near numbers?

No, and that is the point of the game. Each one is generated by applying a single named mistake to the correct answer: writing the pair out additively (IIII instead of IV), reversing it (XI instead of IX), dropping its small letter (X instead of IX), stacking two small letters (IIX), subtracting from the wrong letter (IV instead of IX), or using the same pair one rung too high (XL instead of IV). Pick one and the game prints the rule it breaks and what it really reads as. There is never more than one right answer: the number is chosen first and its numeral is derived from it by the standard algorithm, then every value the round can deal is round-tripped back through the reader before the board exists.

Is there any money, betting or in-app purchase in this?

None, and there never will be. No currency, nothing to buy, no hints to unlock for a fee, no prizes.

Does it work offline?

Yes. Once the page has loaded once, the whole game — the numerals, the wrong-answer rules and the explanations — is on your device. No server is involved in play at any point.

Can I play it with a keyboard or a screen reader?

Both. Arrows move between the four answers and Enter commits one. Every answer is a real button that announces its position and its content, with numerals spelt out letter by letter so XLIX is read as X, L, I, X rather than as a word. A ruled-out answer announces itself as ruled out, carries a ✕ and is struck through, so nothing on the board depends on telling two colours apart.

Numbers run from 1 to 1999, so a numeral never carries more than one M and stays short enough to read at a glance. Every number dealt has at least one subtractive pair in it — that is the whole teaching payload, and it is also what guarantees the wrong answers can be derived from a rule rather than invented. Zero, fractions and the medieval variants (the bar over a letter for thousands, IIII on clock faces) are outside the standard system and are not covered. The move budget is eight plus two to five spare, worked out from how much reading each numeral in the round actually takes rather than from a fixed number.

Prime Sweep and Number Span are the other number-family games here — one turns on divisibility, the other on holding a sequence. Quick Count is the closest in shape: a short round of exact answers under a budget.

Bookmark this page (Ctrl+D, or ⌘D on Mac) or install the app — it works offline the next time you need it.