Roman Numeral Converter
Convert numbers to Roman numerals and Roman numerals back to numbers.
Good to know. The Romans had no numeral for zero, and did their actual sums on an abacus, not in numerals.
How it works
In plain words
Write the number with the largest values first: M = 1000, D = 500, C = 100, L = 50, X = 10, V = 5, I = 1. A smaller numeral before a larger one is subtracted, but only in six pairs: IV = 4, IX = 9, XL = 40, XC = 90, CD = 400 and CM = 900.
The formula
M 1000 · D 500 · C 100 · L 50 · X 10 · V 5 · I 1 IV 4 · IX 9 · XL 40 · XC 90 · CD 400 · CM 900
Worked example
2026 is 2000 + 20 + 6: MM for 2000, XX for 20 and VI for 6, so MMXXVI.
Sources
No outside data or rates: this is plain arithmetic.
4 automated tests check its answers on every change.
About the roman numeral converter
Roman numerals are still everywhere: on clock faces, in film credits and book chapters, after the names of kings and popes, in the Super Bowl, and in tattoos of important dates. This converter works both ways: type a number to get the numerals, or type numerals to get the number.
Seven letters do all the work: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500 and M = 1000. Numerals are written from largest to smallest and added up, so VIII = 5 + 1 + 1 + 1 = 8. A letter can be repeated up to three times.
For 4s and 9s, a smaller numeral goes in front of a larger one and is subtracted: IV = 4 and IX = 9, XL = 40 and XC = 90, CD = 400 and CM = 900. Only these six pairs are allowed, so 99 is XCIX, not IC, and 1999 is MCMXCIX. Clock faces sometimes show 4 as IIII, a tradition rather than a rule.
Standard numerals go up to 3,999 (MMMCMXCIX). The Romans wrote larger numbers with a bar over a numeral to multiply it by 1,000, but that notation varies, so this converter stops at 3,999. There is no Roman numeral for zero.
Questions people ask
What is 2026 in Roman numerals?
MMXXVI: MM for 2000, XX for 20 and VI for 6.
How do you write 4 in Roman numerals?
IV, one before five. Some clocks show IIII instead, but IV is the standard form.
What is the largest Roman numeral?
In standard form, MMMCMXCIX, which is 3,999. Larger numbers used a bar over the numerals.
How do I write a date in Roman numerals?
Convert the day, month and year separately and join them with dots: 14 July 2026 is XIV.VII.MMXXVI.