Roman Numerals Explained: Chart, Rules and Examples

Roman numerals use seven letters to write numbers: I, V, X, L, C, D and M. You build a number by adding symbols from largest to smallest — except in a few cases where a smaller symbol sits before a larger one to mean subtraction. Once you know the seven values and the subtractive pairs, you can read or write almost any number.

How Roman numerals work

Most of the time you add. You write the largest values first and keep adding smaller ones until you reach the number. For example, MMXV is 1,000 + 1,000 + 10 + 5 = 2,015. A symbol can repeat up to three times in a row (III = 3, XXX = 30), but never four — that is where the subtractive rule takes over.

The subtractive rule

To avoid four identical symbols, a smaller value placed before a larger one is subtracted. There are exactly six of these pairs:

• •IV = 4 (5 − 1) and IX = 9 (10 − 1).
• •XL = 40 (50 − 10) and XC = 90 (100 − 10).
• •CD = 400 (500 − 100) and CM = 900 (1,000 − 100).
• •So 49 is XLIX (40 + 9), not IL, and 99 is XCIX (90 + 9), not IC.

Common numbers at a glance

• •1–10: I, II, III, IV, V, VI, VII, VIII, IX, X.
• •40 = XL · 50 = L · 90 = XC · 100 = C.
• •400 = CD · 500 = D · 900 = CM · 1,000 = M.
• •2024 = MMXXIV · 2025 = MMXXV.

The rules and limits

• •Symbols are written from highest to lowest value, left to right.
• •I, X, C and M may repeat up to three times; V, L and D never repeat.
• •Only I, X and C are used subtractively, and only before the next one or two larger symbols.
• •There is no zero and no fractions, and standard Roman numerals stop at 3,999 (MMMCMXCIX).

Turning a number into Roman numerals

1. 1Break the number into thousands, hundreds, tens and units.
2. 2Convert each part using the chart — e.g. 2,024 → 2,000 (MM) + 20 (XX) + 4 (IV).
3. 3Write the parts in order, largest first: MMXXIV.
4. 4Check that no symbol repeats more than three times and every subtractive pair is valid.