Roman Numeral Birthday

Get your date of birth in Roman numerals, formatted the way tattoo artists ink it. Enter your birthday above to see your numerals in three styles, with a part-by-part breakdown you can show your artist before anything is permanent.

Roman numerals use seven basic symbols, and every date is built from them. The tool converts the day, the month and the year separately, then joins them with dots, slashes or dashes.

How the Tool Works

Fill in your birth date as month, day and year, or use the “Show date picker” link to open the native picker. Four quick chips sit below the form: 25 January 1990, 1 January 2000, 31 December 1999, and 14 May 1990. Each one calculates at once.

Enter nothing and the tool replies: “Please enter your date of birth.” An impossible date, 31 February for example, gets the reply: “That date is not valid. Please use a 4-digit year.” A year past 3999 is answered with: “Roman numerals only go up to 3999. Please enter a year up to 3999.”

The result is a big line in dots style, with two supporting lines underneath, one for slashes and one for dashes, and three stats showing the day, the month and the year separately.

For the test date, 14 May 1990, the big line reads XIV · V · MCMXC, the slashes line reads XIV / V / MCMXC, and the dashes line reads XIV – V – MCMXC.

The three stats read XIV, V and MCMXC. There is no copy button: the three styles are plain text on the page, ready to copy by hand.

Roman Numeral Symbols

Roman numerals use seven basic symbols. Every date is built from these:

How It Works: Worked Example

Let us convert January 25, 1990 step by step. Each part of the date (day, month, year) is converted separately. Day: 25. 25 = 10 + 10 + 5 = X + X + V = XXV.

Month: January (1). 1 = I. Year: 1990. 1990 = 1000 + (1000 – 100) + (100 – 10) = M + CM + XC = MCMXC. Full date: XXV · I · MCMXC.

The subtractive rule is key: when a smaller value comes before a larger one, you subtract (IV = 4, IX = 9, XL = 40, XC = 90, CD = 400, CM = 900). Without it, 1990 would be the clumsy MDCCCCLXXXX.

The Rules

The seven symbols I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1000. The six subtractive pairs IV = 4, IX = 9, XL = 40, XC = 90, CD = 400, CM = 900.

Only I, X, and C subtract: I precedes V and X; X precedes L and C; C precedes D and M. V, L, and D never subtract and never repeat.

Repetition limit: no symbol repeats more than three times, which is why 4 is IV and not IIII. The maximum standard value is 3999 = MMMCMXCIX; no standard symbol exists for 5,000 and above, though the vinculum, a bar over a numeral, multiplies it by 1,000, as the section below explains.

The clock-face exception: many clock dials use IIII for 4. That is a visual-balance tradition, not the standard rule. Do not copy clock faces for tattoos.

Year decomposition: break the year into thousands, hundreds, tens, ones: 1994 = M + CM + XC + IV = MCMXCIV. One subtractive step per place value, never stacked. So 99 is XCIX, not IC, and 49 is XLIX, not IL: a symbol can only be subtracted from the next two steps above it.

Reading Roman Numerals Back

The tool converts one way only, from numbers to Roman numerals. To read a Roman numeral back, work it by hand: go from left to right, and if a symbol is smaller than the symbol after it, subtract it; otherwise add it.

MCMXCIV = M (1000) + CM (900) + XC (90) + IV (4) = 1994. MMMCMXCIX = MMM (3000) + CM (900) + XC (90) + IX (9) = 3999.

XIV = X (10) + IV (4) = 14. XXIX = XX (20) + IX (9) = 29. MDCCLXXVI = M (1000) + DCC (700) + LXX (70) + VI (6) = 1776.

The Three Date Orders

The tool always gives day, month, year. Rivals let you pick the order, and the order matters for a tattoo, because Roman numerals give no visual hint about which number is the day and which is the month.

For the test date, 14 May 1990, the three orders are: day, month, year, XIV · V · MCMXC; month, day, year, V · XIV · MCMXC; year, month, day, MCMXC · V · XIV.

Day, month, year is common in Europe and much of the world, while month, day, year is the usual format in the United States.

Decide the order before you show the artist, and check it twice: V · XIV · MCMXC and XIV · V · MCMXC are different dates, and the tool will not warn you.

Famous Birthdays in Roman Numerals, with Tattoo Checks

Each row pairs a famous date with the mistake tattoo buyers most often make.

Common Mistakes

IIII vs IV: clock faces often use IIII for 4, but the correct subtractive form is IV. For birthday tattoos, use IV.

Converting the whole date as one number: do not try to convert 1/25/1990 as a single value. Convert day, month, and year separately, then join them with dots, slashes, or dashes.

Subtracting from too far away: 1999 is MCMXCIX, not IMM. Only one smaller symbol can precede a larger one, and only from the next two steps above it. 49 is XLIX, not IL, and 99 is XCIX, not IC.

Repeating V, L or D: 10 is X, not VV, and 45 is XLV, not VL. V, L and D never repeat and never lead a subtraction.

Years Above 3999 and the Vinculum

The standard system tops out at 3999 = MMMCMXCIX, because M appears at most three times. For larger values, a historical convention called the vinculum places a bar over a numeral to multiply it by 1,000.

V with an overline is 5,000 and X with an overline is 10,000, so 5,015 is V with an overline followed by XV, and the system can extend to 3,999,999. Cajori himself documented the overline: “The thousand-fold value of a number was indicated in some instances by a horizontal line placed above it.”

The tool does not use the vinculum. A year past 3999 is refused with: “Roman numerals only go up to 3999.

Please enter a year up to 3999.” That is honest, because the overline is not consistently supported in fonts, tattoo stencils, engraving systems or ordinary web text. A birth year above 3999 does not exist in practice, so the limit costs nothing here.

One more correction belongs here. Cajori, in A History of Mathematical Notations, claimed that subtractive notation appeared only in the Middle Ages, and that there were no historical examples of the subtractive form for 4.

Modern research shows otherwise: the cenotaph of Marcus Caelius, a Roman centurion who fell in the Battle of the Teutoburg Forest in 9 CE, writes the Eighteenth Legion as XIIX rather than XVIII, a double subtraction, two units from twenty, which goes beyond the rules used today.

The Fasti Antiates Maiores calendar, created between 84 and 55 BCE, has earlier examples still. Subtractive notation was used in ancient Rome, inconsistently and never standardised, and it became dominant only with the printing press, more than a thousand years after the fall of the western Roman Empire.

How This Calculator Compares

Three date-to-Roman-numeral converters rank for the same query, and each one adds something this page does not. The table below lines them up side by side.

Where this converter stops: it converts one way only, it gives one date order, and it refuses years past 3999. CodingMarble converts both ways; MiniWebTool and RevisionTown let you pick the order and the separator; RevisionTown explains the vinculum.

What only this page gives you is the 1-to-100 table, the famous-birthdays tattoo checks, and the history of the subtractive rule, all worked by hand in the guide.

Keep Exploring

Birthday Calculator: count down to your next birthday, with the days left, the age you will turn, and your birthday’s weekday for the next ten years.

Days Lived Calculator: see how many days old you are, with the day-count milestones and the live hours, minutes and seconds ticking.

Golden Birthday Calculator: find your golden birthday, the day your age matches your birth day, with the double and triple birthdays too.

Half Birthday Calculator: find the date halfway to your next birthday, with its weekday, and the table of school sessions for summer birthdays.

Sources

Wolfram MathWorld: Roman Numerals (the additive and subtractive system, with the seven symbols and the six pairs)

Florian Cajori: A History of Mathematical Notations, Vol. I (1928) (the documented history of the subtractive principle, in A History of Mathematical Notations, 1928, with the caveat that his medieval-origin claim is now challenged)

Imperium Romanum: Subtractive notation in ancient Rome (archaeological evidence of ancient subtractive use, including the XIIX inscription on the cenotaph of Marcus Caelius, 9 CE)

Frequently Asked Questions