🏛️ Roman Numeral Converter
By ToolNimba Editorial Team · Updated 2026-06-19
Type a number or a Roman numeral in either box. The other side updates as you type.
This Roman numeral converter works in both directions. Type a regular number from 1 to 3999 to see it written in Roman numerals, or type a Roman numeral such as MMXXIV to read off its value. The tool uses standard subtractive notation (IV rather than IIII) and validates Roman input as you type, so you always get a clean, correct answer.
What is the Roman Numeral Converter?
Roman numerals are a number system from ancient Rome that uses seven letters: I (1), V (5), X (10), L (50), C (100), D (500) and M (1000). Numbers are built by writing these symbols from largest to smallest and adding them together. So MDCLXVI is 1000 + 500 + 100 + 50 + 10 + 5 + 1 = 1666. The system has no symbol for zero and no place value, so the same letter can repeat to build up a value.
The twist is subtractive notation. To avoid writing four of the same symbol in a row, a smaller symbol placed before a larger one is subtracted instead of added. IV means 5 minus 1 (4), IX means 10 minus 1 (9), XL is 40, XC is 90, CD is 400 and CM is 900. Only I, X and C are used as subtractors, and only before the next one or two larger symbols. This is why 4 is IV and not IIII, and why 1994 is MCMXCIV: M (1000) + CM (900) + XC (90) + IV (4).
Standard Roman numerals run from 1 to 3999. There is no compact way to write zero or negative numbers, and values above 3999 traditionally need an overline (a bar over a letter to multiply it by 1000), which is hard to type and rarely needed today. That is why this converter, like most modern tools, limits the range to 1 through 3999 and uses the additive and subtractive rules that the Romans themselves settled into common use.
When to use it
- Reading the year on a film credit, building cornerstone, or book copyright page written in Roman numerals.
- Writing a chapter number, clock face, or Super Bowl style edition in proper Roman form.
- Checking a tattoo, logo, or monument inscription before it is set in stone, so the numerals are valid.
- Helping a student learn the addition and subtraction rules behind Roman numerals with worked examples.
How to use the Roman Numeral Converter
- To convert a number to Roman numerals, type a whole number from 1 to 3999 in the left box.
- Read the Roman numeral that appears in the right box and in the result line below.
- To convert the other way, type a Roman numeral (any case) in the right box.
- If the Roman numeral is not valid, an inline message explains it; fix it and the value updates.
Formula & method
Worked examples
Convert the number 2024 to Roman numerals.
- 2024 = 1000 + 1000 + 24, so write MM for the two thousands.
- 24 = 10 + 10 + 4, so write XX for the twenties.
- 4 uses subtractive notation: IV (5 minus 1).
- Join them: MM + XX + IV = MMXXIV.
Result: 2024 = MMXXIV
Convert the Roman numeral MCMXCIV to a number.
- M = 1000.
- CM = 900 (C before M means 1000 minus 100).
- XC = 90 (X before C means 100 minus 10).
- IV = 4 (I before V means 5 minus 1).
- Add them: 1000 + 900 + 90 + 4 = 1994.
Result: MCMXCIV = 1994
The seven Roman numeral symbols and their values
| Symbol | Value |
|---|---|
| I | 1 |
| V | 5 |
| X | 10 |
| L | 50 |
| C | 100 |
| D | 500 |
| M | 1000 |
The six subtractive pairs
| Numeral | Value | Meaning |
|---|---|---|
| IV | 4 | 5 minus 1 |
| IX | 9 | 10 minus 1 |
| XL | 40 | 50 minus 10 |
| XC | 90 | 100 minus 10 |
| CD | 400 | 500 minus 100 |
| CM | 900 | 1000 minus 100 |
Common numbers in Roman numerals
| Number | Roman numeral |
|---|---|
| 4 | IV |
| 9 | IX |
| 14 | XIV |
| 40 | XL |
| 49 | XLIX |
| 90 | XC |
| 500 | D |
| 1000 | M |
| 1666 | MDCLXVI |
| 3888 | MMMDCCCLXXXVIII |
| 3999 | MMMCMXCIX |
Common mistakes to avoid
- Writing four of the same symbol in a row. Standard notation never repeats a symbol four times. 4 is IV, not IIII, and 40 is XL, not XXXX. The tool rejects IIII and similar forms as invalid.
- Using the wrong subtractor. Only I, X and C subtract, and only before the next one or two larger symbols. IL for 49 is wrong; the correct form is XLIX. Likewise 99 is XCIX, not IC.
- Repeating V, L or D. The symbols for 5, 50 and 500 are never repeated, because two of them would just equal the next symbol up. VV is not 10; that is X. Similarly LL is C and DD is M.
- Expecting a numeral for zero or for very large values. Roman numerals have no symbol for zero, and standard form stops at 3999 (MMMCMXCIX). Larger values need an overline notation that is outside this tool.
Glossary
- Additive notation
- Building a number by writing symbols from largest to smallest and adding their values, as in MDC = 1600.
- Subtractive notation
- Placing a smaller symbol before a larger one to subtract it, as in IV (4), IX (9) and CM (900).
- Subtractor
- A symbol (only I, X or C) written before a larger symbol so that its value is taken away rather than added.
- Overline (vinculum)
- A bar drawn over a numeral to multiply its value by 1000, used historically for numbers above 3999.
Frequently asked questions
How do I convert a number to Roman numerals?
Type the number (1 to 3999) into the number box and read the Roman numeral that appears. The tool builds it by taking the largest symbol or subtractive pair that fits, then repeating with the remainder.
How do I convert Roman numerals to a number?
Type the Roman numeral into the Roman box and the number appears instantly. The converter adds each symbol but subtracts any symbol that is smaller than the one to its right, like the I in IV.
What is the largest number in Roman numerals?
In standard notation the largest is 3999, written MMMCMXCIX. Larger numbers need an overline to multiply symbols by 1000, which is rarely used, so this tool covers 1 to 3999.
Why is 4 written as IV and not IIII?
Standard Roman numerals avoid repeating a symbol four times. Instead a smaller symbol before a larger one is subtracted, so 4 is IV (5 minus 1). You may still see IIII on some clock faces as a stylistic choice.
Is there a Roman numeral for zero?
No. The Roman system has no symbol for zero and no concept of place value. It was built for counting and recording positive whole numbers, so the smallest value it represents is 1 (I).
Does the converter check whether a Roman numeral is valid?
Yes. It only accepts the letters I, V, X, L, C, D and M and requires a canonical, properly ordered form. Invalid input like IIII, VV or IC is rejected with a short message explaining why.