Roman Numeral Converter
Convert numbers to Roman numerals and back again, in either direction, for values from 1 to 3999 — using correct standard subtractive notation (IV = 4, IX = 9).
Roman Numeral Converter
Roman Numeral
MMXXVI
Standard subtractive form
How It Works
Roman numerals build numbers from seven letters — I (1), V (5), X (10), L (50), C (100), D (500) and M (1000) — combined largest to smallest and added together, with a subtractive rule for certain values. When a smaller symbol appears before a larger one it is subtracted: IV is 4, IX is 9, XL is 40, XC is 90, CD is 400 and CM is 900. The standard system represents whole numbers from 1 to 3999 (there is no symbol for zero, and 4000+ needs an overline convention). This converter works both ways: enter a number to get its Roman form, or enter a Roman numeral to get its value — and it validates that the numeral is written in proper canonical form. It is handy for reading clock faces, book chapters, movie sequels, monarch names and copyright dates.
Formula
Symbols: I=1, V=5, X=10, L=50, C=100, D=500, M=1000. Subtractive pairs: IV=4, IX=9, XL=40, XC=90, CD=400, CM=900.
Frequently Asked Questions
How do Roman numerals work?
Seven letters (I, V, X, L, C, D, M) are combined from largest to smallest and added. A smaller symbol before a larger one is subtracted, so IV = 4 and IX = 9.
What is the largest number in Roman numerals?
In the standard system, 3999 (MMMCMXCIX). Larger numbers require an overline (vinculum) to multiply a symbol by 1000, which this converter does not use — it covers 1 to 3999.
Why is 4 written as IV, not IIII?
Standard notation uses the subtractive form IV (5 − 1) rather than IIII. (Clock faces are a common traditional exception that use IIII for symmetry.) The converter uses the standard IV.
Is there a Roman numeral for zero?
No — the Roman system has no symbol for zero. It represents positive whole numbers only, which is why it starts at I (1).
How do I convert a Roman numeral to a number?
Switch the calculator to “Roman → Number”, type the numeral (e.g. MMXXVI), and it returns the value (2026), after checking the numeral is written in valid form.