Roman Numeral Mistakes to Check Before a Tattoo or Engraving

Most Roman numeral mistakes come from subtracting the wrong way. Only six subtractive pairs are standard, IV, IX, XL, XC, CD and CM, so you can't take I away from C to make 99 or X from M to make 990. Before anything permanent, run your number through a converter that validates the form, and decide on the date order (day first or month first) yourself.

The rules in one minute

Roman numerals use seven letters:

I	V	X	L	C	D	M
1	5	10	50	100	500	1000

Standard form follows four rules:

1. Write from largest to smallest and add. VIII = 5 + 3 = 8. MMXXVI = 1000 + 1000 + 10 + 10 + 5 + 1 = 2026.
2. Repeat I, X, C and M at most three times. 3 is III, but 4 is IV, not IIII.
3. Never repeat V, L or D. VV isn't 10, it's X.
4. Subtract only in the six standard pairs. A smaller numeral placed before a larger one is subtracted, but only I before V or X, X before L or C, and C before D or M. And only one numeral can be subtracted at a time.

Rule 4 is where nearly every error happens.

Six numbers people get wrong

Number	Wrong	Right	Why
4	IIII	IV	Four repeats aren't allowed
49	IL	XLIX	I can only be subtracted from V or X. Write 40 + 9
99	IC	XCIX	Write 90 + 9
990	XM	CMXC	Write 900 + 90
1990	MXM	MCMXC	1000 + 900 + 90
8	IIX	VIII	You can't subtract two numerals

The trick that fixes most of these is to break the number into its decimal places and convert each one separately. For 1999: 1000 = M, 900 = CM, 90 = XC, 9 = IX, giving MCMXCIX. For 1984: M + CM + LXXX + IV = MCMLXXXIV.

Are clock faces wrong, then?

Not exactly. Many clocks use IIII for four, a long-standing design choice that balances the dial visually against VIII on the other side. You'll also see unusual forms on old buildings and manuscripts, because the rules weren't fully standardized in Roman times. But for anything people will read and check today, including tattoos, rings, cornerstones and book copyright dates, use the standard form. Someone will notice.

How should you write a date?

Convert the day, month and year separately and join them with dots (or dashes, or spaces). The year is the long part. Months and days are short.

The order is a choice you need to make on purpose:

Date	Day.Month.Year	Month.Day.Year (US)
October 7, 2026	VII.X.MMXXVI	X.VII.MMXXVI
June 14, 2025	XIV.VI.MMXXV	VI.XIV.MMXXV
December 31, 1999	XXXI.XII.MCMXCIX	XII.XXXI.MCMXCIX

Notice that the first row is ambiguous: VII.X could be July 10 or October 7, depending on the convention the reader assumes. If the date matters, consider writing the month as a word ("7 October MMXXVI") or adding a small note on the order for whoever does the engraving.

Limits worth knowing

• There's no zero. Romans didn't write zero as a numeral, and the converter starts at 1.
• The standard range ends at 3999 (MMMCMXCIX). Larger numbers used a bar over the letters to multiply by 1,000, but there's no single agreed way to type that, so converters stop at 3999.
• No fractions or negatives. Roman numerals are whole, positive numbers.

Checking a numeral with the converter

The Roman Numeral Converter works in both directions and catches the mistakes above:

1. In Number (1–3999) or Roman numeral, type either a number (1990) or a numeral (MCMXC). The direction is detected automatically, and lowercase letters are fine.
2. If you type a non-standard form, the converter tells you it isn't valid and suggests the standard version. IC gets "did you mean XCIX?", IIII gets IV, and MXM gets MCMXC.
3. For dates, use the date picker under Date in Roman numerals. You'll get both Day.Month.Year and Month.Day.Year (US) versions, each with a copy button.
4. Open the Roman numeral chart for a quick reference of the seven letters and six subtractive pairs.

A useful habit before a tattoo appointment: convert the date, then paste the result back in and check it converts to the number you expect. The validation runs instantly in your browser.

FAQ

Why does the converter reject my numeral?

You've probably used a non-standard subtraction or too many repeats. VX looks like "5 before 10", but it isn't a valid way to write 5, and XXXX should be XL. The converter flags these and suggests the standard form instead of silently accepting them.

Should the year in a date be written in full?

Yes. Abbreviating 2026 to XXVI (for '26) is possible, but readers will take it as the number 26. Most people write the full MMXXVI.

How do I write 2000?

MM. Every year from 2000 to 2099 starts with MM.

For spelling numbers out in words instead, try the Number to Words converter. To double-check a numeral, use the Roman Numeral Converter.