Roman Numeral Converter
Numbers to Roman numerals and back, with checks and steps. Runs in your browser.
About this roman numeral converter
This Roman numeral converter turns numbers into Roman numerals and Roman numerals back into numbers, in one box. Type 2026 and you get MMXXVI. Type MCMXCIV and you get 1,994. It is for students, writers, designers and anyone about to engrave a date.
It also checks your numeral. If you type IIII, IC or VX, you get the value it would usually be read as, a plain explanation of the rule it breaks, and the standard spelling with a button to switch to it. Every result comes with a step-by-step breakdown, so you can see how MCMLXXXVII adds up to 1987.
Standard numerals stop at 3,999. Turn on large numbers and the tool writes up to 3,999,999 with a bar over the thousands, using a real combining overline so the bars survive copy and paste. There is also a date mode for birthdays, weddings and tattoo designs.
Features
Both directions, one input
Digits convert to a Roman numeral and letters convert to a number. Lowercase works, and separators like 1,987 or 1 987 are ignored.
Explains what is wrong
Non-standard numerals get a Not standard label and a reason: a symbol repeated four times, V, L or D repeated or subtracted, a symbol subtracted from one too far up (IL, IC, XD), two symbols subtracted at once (IIX), or a symbol out of order after a pair (IXI).
Step-by-step breakdown
Number to Roman splits the value into thousands, hundreds, tens and ones and shows each piece. Roman to number lists each group, says whether it adds or is a subtractive pair like CM (1000 − 100), and shows the total.
Large numbers with a vinculum
Switch on bar notation to write up to 3,999,999. A bar multiplies a letter by 1,000, so 5,000 is V̅. The copied text uses the combining overline U+0305, and pasting it back in reads correctly.
Dates in Roman numerals
Pick a date, choose month-first, day-first or year-first order, and choose a dot, middle dot, bullet, slash, hyphen or space between the parts. 30 October 2026 in US order is X.XXX.MMXXVI.
Symbol chart and examples
A chart of the seven letters sits below the result, with the ×1,000 values shown in bar mode.
How to use the roman numeral converter
- 1Type a number or a Roman numeral. The direction is detected for you.
- 2Read the result and the step-by-step breakdown, or switch to Date to Roman.
- 3Fix any non-standard numeral with the suggested form, then copy.
When to use it
Tattoos and engravings
Write a birth or wedding date in the order the person actually uses, then copy it exactly.
Reading copyright years
Film credits and old books often print the year as a numeral such as MCMXCIX. Paste it in to get 1999.
Homework and teaching
Students can test their own answers and see the rule they broke. Teachers can load IC or IIX to show why those spellings are not used.
How do Roman numerals work?
Seven letters carry the values: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500 and M = 1,000. You write the largest values first and add them up, so MDCLXVI is 1,000 + 500 + 100 + 50 + 10 + 5 + 1 = 1,666.
To avoid four of the same letter in a row, a smaller letter placed before a larger one is subtracted. Only six of these pairs are standard: IV (4), IX (9), XL (40), XC (90), CD (400) and CM (900). Convert one place value at a time and you rarely go wrong. 1987 is 1000 + 900 + 80 + 7, which gives M + CM + LXXX + VII = MCMLXXXVII.
What are the rules for a valid Roman numeral?
The modern standard form follows a few strict rules. Breaking any of them gives a numeral that people can often still read, but that is not the accepted spelling.
- I, X, C and M can repeat up to three times in a row. V, L and D never repeat.
- Only I, X and C are subtracted, and only from the next two larger letters: I from V and X, X from L and C, C from D and M.
- Only one smaller letter can stand before a larger one. 8 is VIII, not IIX.
- After a subtractive pair, the next letter must be smaller than the one subtracted. 10 is X, not IXI.
- Every number from 1 to 3,999 has exactly one standard spelling.
How do you write numbers bigger than 3,999?
With only the seven letters, the largest standard numeral is MMMCMXCIX, which is 3,999. Romans and later writers handled bigger values with a vinculum, a bar over a letter that multiplies it by 1,000. V̅ is 5,000, X̅ is 10,000 and M̅ is 1,000,000.
This tool writes the thousands part with bars and the rest normally, so 4,000 is I̅V̅ and 3,999,999 is M̅M̅M̅C̅M̅X̅C̅I̅X̅CMXCIX. You will see other conventions in old sources, such as MMMM for 4,000, so the tool explains those as non-standard rather than rejecting them.
Why use Mavros
| Mavros | Typical upload sites | |
|---|---|---|
| Direction | Detects number or numeral from what you type | Separate boxes or a Convert button |
| Invalid numerals | Explains the broken rule and offers the standard form | Silently accepted or a bare error |
| Working shown | Place values or add and subtract steps for every result | Answer only |
| Above 3,999 | Up to 3,999,999 with a real overline that copies | Capped at 3,999, or bars that do not copy |
| Dates | Built in, three orders and six separators | Often a separate page |
Tips
- Clock faces often show 4 as IIII. That is a long design tradition, but the standard numeral is IV, and the tool says so.
- There is no Roman numeral for zero. Medieval scholars sometimes wrote N, short for nulla.
- Type plain letters, not the Unicode Roman numeral characters (U+2160 to U+2188). The tool reads only I, V, X, L, C, D and M.
- For a date tattoo, confirm the order first. Americans usually write month first, most other countries day first.
- Need the same date in the Hijri or Bengali calendar too? Convert it between calendars first, then write the numbers here.
- Need a number spelled out in words instead? Try Number to Words, which also writes amounts for checks.
- Working out how many years ago a Roman-numeral date was? Convert it here, then use the age calculator for the exact span.
Questions
What is 2026 in Roman numerals?
2026 is MMXXVI: MM for 2,000, XX for 20 and VI for 6. Type any year into the box to get its numeral and a place-by-place breakdown.
What is the largest Roman numeral?
The largest standard Roman numeral is MMMCMXCIX, which is 3,999. With a bar over letters to multiply by 1,000, this tool goes up to 3,999,999.
Why is 4 written IV and not IIII?
The standard rule allows a letter at most three times in a row, so 4 is written as 5 minus 1, IV. IIII appears on many clock faces and in some old inscriptions, but it is not the standard form.
Is IC a valid way to write 99?
No. I can only be subtracted from V and X, so 99 is written XCIX, which is 90 plus 9. The tool reads IC as 99 but marks it as not standard and offers XCIX.
Is there a Roman numeral for zero?
No, the Roman system has no zero. Some medieval writers used the letter N, from the Latin nulla, meaning none. Typing 0 here gives a short explanation instead of a result.
How do I write a date in Roman numerals?
Convert the day, month and year separately and join them with a separator. Switch to Date to Roman, pick the date, the order and the separator, then copy the result, for example X.XXX.MMXXVI.
How do I type a bar over a Roman numeral?
Put the combining overline character U+0305 right after the letter. The easiest way is to turn on large numbers, convert the value here and copy it. The bar is part of the copied text.
Is anything I type sent to a server?
No. Conversions and checks run in your browser and nothing is uploaded or saved. For other number formats, try the number base converter for binary and hex.