Everyday Tools
Roman Numeral Converter
Switch direction to convert an ordinary number into Roman numerals, or read a Roman numeral back as a number.
Calculation inputs
Standard Roman numerals cover 1 to 3,999.
Results
No result yet
Complete the fields and select Calculate to show results here.
About this calculator
This converter switches numbers into Roman numerals and reads Roman numerals back into ordinary numbers. It is handy for checking clock faces, movie copyright years, book chapter headings, or historical dates.
How the calculation works
- Symbols: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1000
- Subtractive pairs: IV, IX, XL, XC, CD, CM
- Values are built largest first, subtracting where a smaller symbol precedes a larger one
Notes and assumptions
Standard Roman numerals have no zero and no symbol above 1,000, so the practical range is 1 to 3,999.
How it works in plain English
Standard Roman numerals use seven letters, each with a fixed value: I for 1, V for 5, X for 10, L for 50, C for 100, D for 500, and M for 1,000. To write a number, the converter works from the largest value down, repeating or combining symbols to build up the total, such as III for 3 or LX for 60.
Six special two-letter combinations subtract rather than add: IV (4), IX (9), XL (40), XC (90), CD (400), and CM (900). These exist so that no symbol is ever repeated more than three times in a row, which is why 4 is written IV instead of IIII.
Converting the other direction — from Roman numerals back to a number — reads the symbols left to right, adding each value unless a smaller symbol precedes a larger one, in which case it is subtracted. Standard Roman numerals only cover whole numbers from 1 to 3,999, since there is no widely agreed symbol for zero or for numbers at or above 4,000.
Worked example
Converting 2,026 to Roman numerals: 2,026 breaks down as 2,000 (MM) + 20 (XX) + 6 (VI), giving MMXXVI. Going the other way, reading MMXXVI: M+M=2,000, X+X=20, V+I=6, adding up to 2,026. A trickier case is 1,994, which breaks into 1,000 (M) + 900 (CM) + 90 (XC) + 4 (IV), giving MCMXCIV — a good illustration of how the subtractive pairs keep the numeral shorter than writing nine or four individual symbols. Reading MCMXCIV back the other direction confirms the total: M=1,000, then CM (C before M, so subtract) contributes 900, XC contributes 90, and IV contributes 4, which sums to 1,994 and matches the original number exactly. This back-and-forth check is a useful way to verify that a numeral has been built correctly before using it in a date or heading.
Roman numeral symbol values
| Symbol | Value |
|---|---|
| I | 1 |
| V | 5 |
| X | 10 |
| L | 50 |
| C | 100 |
| D | 500 |
| M | 1,000 |
Frequently asked questions
Why is 4 written as IV instead of IIII?
The subtractive rule limits any symbol to appearing no more than three times in a row, so IIII is not standard. Placing a smaller symbol before a larger one, as in IV, signals subtraction instead, giving 5 minus 1. This convention keeps numerals shorter and easier to read at a glance.
What is the largest number Roman numerals can represent?
Using the standard letters and subtractive pairs, numerals top out at 3,999, written MMMCMXCIX. There is no standard single symbol for 4,000 or higher without extending the system with bars or brackets over letters to multiply their value, which most modern uses do not include.
Is there a Roman numeral for zero?
No. The Roman numeral system was developed without a concept of zero as a standalone number, so there is no symbol for it. Any conversion attempt involving zero, or numbers outside the 1 to 3,999 range, falls outside what standard Roman numerals can represent.
Why do some clocks show IIII instead of IV for four o'clock?
This is a longstanding decorative and historical convention on clock faces, not a numeral rule violation. Several theories exist for why it stuck, including visual symmetry with VIII on the opposite side of the dial, but it remains an exception rather than the standard subtractive form.
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