A roman numeral converter changes ordinary numbers into Roman numerals and Roman numerals back into numbers. Formula: to roman: greedy map M,CM,D,CD,C,XC,L,XL,X,IX,V,IV,I. from roman: subtractive scan of MDCLXVI. 2026 is MMXXVI, and MCMXCIX is 1999.
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How to use the roman numeral converter
- Choose number to Roman or Roman to number.
- Enter a whole number from 1 to 3,999, or a Roman numeral.
- Read the converted value.
How the roman numeral converter works
The roman numeral converter works in both directions. To convert a number to Roman numerals, it takes the largest value from the list M (1,000), CM (900), D (500), CD (400), C (100), XC (90), L (50), XL (40), X (10), IX (9), V (5), IV (4) and I (1) that fits, writes it down, subtracts it, and repeats until nothing is left. To read a Roman numeral, it adds each symbol’s value but subtracts a symbol that comes before a larger one. Standard numerals cover 1 to 3,999.
The seven symbols
Roman numerals use seven letters: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500 and M = 1,000. There is no symbol for zero and no place value. Symbols are written from largest to smallest and added, so LXI is 50 + 10 + 1 = 61. Up to three identical symbols can stand together, as in III or CCC, but V, L and D are never repeated.
Subtractive notation
Instead of writing four identical symbols, standard notation places a smaller symbol before a larger one to subtract it. There are only six such pairs: IV (4), IX (9), XL (40), XC (90), CD (400) and CM (900). I is subtracted only from V and X, X only from L and C, and C only from D and M. So 99 is XCIX, not IC, and 49 is XLIX, not IL. The roman numeral converter always writes this standard form.
Roman numeral converter worked example
To write 2026, take MM for 2,000, then XX for 20, then VI for 6: MMXXVI. To write 1999, take M (1,000), CM (900), XC (90) and IX (9): MCMXCIX. To read CDXLIV, add CD (400), XL (40) and IV (4) to get 444. The largest standard value, 3,999, is MMMCMXCIX.
| Number | Roman numeral |
|---|---|
| 2026 | MMXXVI |
| 1999 | MCMXCIX |
| 444 | CDXLIV |
| 3999 | MMMCMXCIX |
| 14 | XIV |
| 90 | XC |
Checking a numeral you were given
The converter reads numerals by adding and subtracting symbol values, and it is strict: it accepts only standard forms from I to MMMCMXCIX. Non-standard forms such as IIII, VX, IC or VV get an error message instead of a number. Clock faces often show 4 as IIII, and old inscriptions mix forms, so when reading one of those, rewrite it in standard form first: IIII becomes IV and IC (99) becomes XCIX.
Where Roman numerals are used today
You will see Roman numerals on clock faces, in the names of monarchs and popes, in book chapters and front matter, in outlines, in movie copyright dates and in the numbering of major sporting events. Copyright years in film credits are a common reason to use a roman numeral converter: MCMLXXXV is 1985. Lowercase forms such as iv and xii number the preface pages of many books.
Numbers above 3,999
Classical notation had no standard way to write very large values. One later convention places a bar, called a vinculum, over a numeral to multiply it by 1,000, so V with a bar is 5,000. Because bars are hard to type and not universally recognized, the tool limits itself to 1 through 3,999. Zero, negative numbers and fractions have no standard Roman form.
Tips
- Use the six subtractive pairs only.
- Never repeat V, L or D.
- Write at most three identical symbols in a row.
- Round-trip a numeral to check that it is standard.
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Sources
OpenStax Contemporary Mathematics, 4.2: Early numeration systems; Language Portal of Canada: Numbers – Roman numerals.
Formula and method
To Roman: repeatedly take the largest value from M 1000, CM 900, D 500, CD 400, C 100, XC 90, L 50, XL 40, X 10, IX 9, V 5, IV 4, I 1. From Roman: add values, but subtract a symbol that comes before a larger one.
Standard subtractive Roman notation for 1-3999. Does not support overlines for thousands beyond that range.
Questions about this calculator
What is 2026 in Roman numerals?
MMXXVI.
What is the largest standard Roman numeral?
MMMCMXCIX, 3,999.
Is IIII correct for 4?
The standard form is IV; IIII appears on some clocks, and this tool rejects it.
Is there a Roman numeral for zero?
No.
Which symbols can be subtracted?
Only I, X and C.
Check the assumptions and units before relying on a result. Financial, tax and health estimates do not replace advice for your individual circumstances.
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