Long before the digits we use today, the Romans wrote numbers with letters. Just a handful of symbols do most of the work:

To read a numeral you usually add the symbols from left to right. So \text{VII} is 5 + 1 + 1 = 7, and \text{XVI} is 10 + 5 + 1 = 16. The symbols are written biggest-first, much like the columns in place value.

There is one neat twist. When a smaller symbol sits before a larger one, you subtract it instead of adding. That is how four and nine are written:

So order matters: \text{VI} is six (five then one more), but \text{IV} is four (one less than five). With those few rules you can read and write all the small numbers.

Press play to turn a random number into its Roman numeral, one symbol at a time. Replay it to get a different number each time.

Khan Academy introduces Roman numerals here: