Free Roman Numeral Converter
Convert numbers 1–3,999 and dates to Roman numerals and back, with overline support to 3,999,999, step-by-step breakdowns and malformed numeral checks.
Loading tool…
How to convert numbers and dates to Roman numerals and back
Convert numbers to Roman numerals and back, up to 3,999,999 with overlines, with a step-by-step breakdown and Roman dates.
- Choose Number → Roman, Roman → Number or Date → Roman.
- For numbers, type digits. Tick Allow overline for values above 3,999, and optionally write the overlined part in [brackets] for plain text.
- For numerals, type letters in upper or lower case. Invalid input lists every rule it breaks and suggests the correct form.
- For dates, pick the date, the order (day-month-year, month-day-year or year-month-day) and a separator.
- Copy the numeral, number or date with one click.
When you need Roman numerals
Roman numerals still turn up everywhere: clock faces, book chapters and appendices, monarchs and popes, film copyright years, sporting events, building foundation stones, outline headings and, increasingly, tattoos and engraved jewellery with a meaningful date. Getting them right matters most when the result is permanent.
Students meet them in maths and history classes, designers need them for invitations and watch faces, and anyone reading an old book or monument occasionally needs to decode one. The validation mode is especially useful for checking a numeral someone else wrote.
Worked examples
1994 converts to MCMXCIV. The breakdown shows each place value: 1,000 = M, 900 = CM, 90 = XC and 4 = IV. The year 2026 is MMXXVI: two thousands, two tens, one five and one one.
With Allow overline ticked, 4,250 becomes I̅V̅CCL: the overlined IV means 4 × 1,000, followed by CC (200) and L (50). In bracket notation it is written [IV]CCL. The largest supported number, 3,999,999, is M̅M̅M̅C̅M̅X̅C̅I̅X̅CMXCIX.
Going the other way, IC is rejected with an explanation: I may only be placed before V or X. Read with the add-and-subtract rule it would be 99, which is correctly written XCIX. IIII is flagged because no letter may appear more than three times in a row, with IV suggested instead. Finally, the date 30 October 2026 in day.month.year order is XXX.X.MMXXVI.
How the conversion and validation work
Numbers are split into thousands, hundreds, tens and ones. Each digit is written with the symbols for its place: for example, 4 is IV, 40 is XL and 400 is CD; 9 is IX, 90 is XC and 900 is CM. Joining the parts gives the standard form, so there is exactly one correct numeral for each number from 1 to 3,999.
For larger numbers the vinculum convention is used: the thousands are written as a standard numeral with a bar over each letter, which multiplies it by 1,000, followed by the standard numeral for the remainder. Numbers below 4,000 keep their M-based form.
Reading a numeral, the converter checks the standard rules: only I, V, X, L, C, D and M; V, L and D are never repeated; I, X, C and M appear at most three times in a row; only IV, IX, XL, XC, CD and CM are allowed subtractions; and parts must run from largest to smallest. Each broken rule produces its own message, and the converter suggests the standard form of the value the numeral was probably meant to be.
Common mistakes to avoid
Writing 99 as IC, 49 as IL or 1990 as MXM looks logical but breaks the subtraction rule; the correct forms are XCIX, XLIX and MCMXC. Another frequent error is in dates: 03.04.2026 means 3 April in most countries but March 4 in the United States, so choose the order deliberately.
Overlines are easily lost when text is copied into another app or font. If the bar matters, use the bracket notation or check how the overlined letters render in the final design before printing or engraving.
Useful tips and limitations
- Before engraving or tattooing, check the date order your reader expects and copy the result rather than retyping it.
- Only I, X and C are used to subtract, and only before the next two larger numerals, which rules out forms like IC or VX.
- Check a tattoo or engraving date by converting it back with Roman → Number before you commit.
- Type lower-case letters if that is quicker; the converter reads them the same way.
Common questions
What is the largest standard Roman numeral?
MMMCMXCIX, which is 3,999. Larger numbers need another notation, such as a bar over a numeral to multiply it by 1,000.
Why is IIII on some clocks?
Clockmakers have long used IIII for four for visual balance. In standard modern notation four is IV, and this converter flags IIII as non-standard.
Is there a Roman numeral for zero?
No. Roman numerals have no symbol for zero, so the converter starts at 1.
How do you write 2026 in Roman numerals?
MMXXVI: MM for 2,000, XX for 20 and VI for 6.
How does the Roman Numeral Converter write numbers above 3,999?
With the overline (vinculum) option it places a bar over the thousands, which multiplies them by 1,000, so 5,000 is V̅ and 4,250 is I̅V̅CCL. It supports values up to 3,999,999.
Why does the converter reject MCMC?
After the subtraction CM (900), the next part must be smaller than C (100). MCMC would mean 2,000 written in a non-standard way; the correct form is MM.
Everything you enter is calculated in your browser. Nothing is uploaded and no account is needed. Copy or download your results before leaving the page.