No zero, no place value, just seven letters and two simple rules — yet this 2,000-year-old system still shows up on clocks, movie titles, and Super Bowl banners today.
Roman numerals don't use place value the way our everyday numbers do — there's no ones column or tens column. Instead, they work through just seven symbols and two clean rules for combining them. Once those two rules click, any Roman numeral becomes readable.
Roman numerals are the number-writing system used in ancient Rome, built from combinations of just seven letters. Unlike the numbers used every day — which rely on place value, where a digit's position changes its worth — Roman numerals work by combining symbols according to a couple of fixed rules.
The system is over 2,000 years old, but it never fully disappeared. It still appears on clock faces, in movie and book credits, for naming monarchs and popes, and in numbering major events like the Super Bowl.
Every Roman numeral, no matter how large, is built from just these seven symbols.
| Symbol | Value |
|---|---|
| I | 1 |
| V | 5 |
| X | 10 |
| L | 50 |
| C | 100 |
| D | 500 |
| M | 1,000 |
When a smaller (or equal) symbol comes after a larger one, add its value.
VI = V (5) + I (1) = 6. XV = X (10) + V (5) = 15. LXVII = L (50) + X (10) + V (5) + I (1) + I (1) = 67.
When a smaller symbol comes before a larger one, subtract the smaller value from the larger one instead of adding it. This is what lets Roman numerals avoid writing the same symbol four times in a row.
IV = V (5) − I (1) = 4. IX = X (10) − I (1) = 9. XL = L (50) − X (10) = 40. CM = M (1,000) − C (100) = 900.
Adding I four times in a row looks like a reasonable way to build 4 — but it breaks the standard repetition limit.
The fix: the standard modern form of 4 is IV, using the subtraction rule. Interestingly, IIII does still appear traditionally on many clock faces — more on that below — but in standard written use, IV is correct.
A symbol can be repeated to add its value, but only up to three times in a row, and only for the symbols I, X, C, and M. The symbols V, L, and D are never repeated — ever.
| Can Repeat (up to 3 times) | Never Repeats |
|---|---|
| I, X, C, M | V, L, D |
III = 3 (three I's, allowed). XXX = 30 (three X's, allowed). But 4 is never written as IIII in standard form, and 10 is never written as VV — instead, the subtraction rule takes over.
Subtraction can't be used freely between just any two symbols — only between specific pairs, one "step" apart in size. A smaller symbol may only subtract from the next one or two symbols above it, never further.
| Smaller Symbol | May Precede (Subtract From) |
|---|---|
| I | V or X only |
| X | L or C only |
| C | D or M only |
| V, L, D | Never used to subtract |
This looks tempting — "one before a hundred" — but I is only allowed to subtract from V or X, never from C.
The fix: 99 must be built in stages: XC (90) + IX (9) = XCIX. Each subtraction pair can only skip one size level, never jump straight from I to C.
Large numbers are built by working from the biggest symbols down to the smallest, taking the biggest possible "bite" at each step.
1994 = 1000 + 900 + 90 + 4 = M + CM + XC + IV = MCMXCIV.
2024 = 1000 + 1000 + 20 + 4 = M + M + XX + IV = MMXXIV.
Tap any Roman numeral below to see its value and exactly how it breaks down, piece by piece.
Tap a Roman numeral above to see its breakdown.
Roman numerals have no symbol for zero at all. The Romans didn't use zero as a number the way modern mathematics does — that concept came from Indian mathematicians centuries later, exactly as covered in our Number Systems article.
Since I, X, C, and M can repeat, it's easy to assume the rule applies to every symbol.
The fix: only I, X, C, and M ever repeat, and never more than three times. V, L, and D each appear at most once in any numeral — if you ever need "two fives," you already have a ten (X), so V is never doubled.
Super Bowl championships are numbered using Roman numerals — Super Bowl LVIII (58) took place in 2024. Movie sequels use them too (Rocky IV), as do monarchs (Queen Elizabeth II) and the copyright years hidden in old film credits.
Many clock faces show 4 o'clock as IIII rather than IV, breaking the standard rule on purpose. Nobody knows for certain why, but one popular theory is that IIII balances visually with VIII on the opposite side of the clock face.
Without extending the notation, the largest standard Roman numeral is 3,999 (MMMCMXCIX) — since M can only repeat three times, and there's no single symbol for 4,000 or higher without adding special marks above the letters.
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