MMCXL
A column topped with a scroll beside the letters I, V and X I V X The library

Learn the letters

Seven letters, a handful of rules, and a long and surprisingly tidy history. Read it straight through, or dip into the chapter you need.

The seven letters

Roman numerals write numbers with seven capital letters. There is no zero and no place value as we know it in ordinary digits: each letter means the same wherever it stands, and the arrangement tells you whether to add or to subtract.

The seven letters and their values
LetterValueA way to remember it
I1One upright stroke, like a tally mark.
V5An open hand with the thumb apart: five digits.
X10Two Vs joined at the point.
L50Half of a hundred; the shape is a worn-down older sign.
C100From the Latin centum, a hundred, as in century.
D500Half of the older sign for a thousand.
M1000From the Latin mille, a thousand, as in millennium.

If you like a mnemonic, read upwards in value: I Value Xylophones Like Cows Dig Milk. It is silly, and silly things stick.

The rules

Modern usage follows seven small rules. Learn them once and you can read, and check, any numeral you meet.

A practical test for any numeral you are unsure about: convert it to a number, then convert the number back using the converter. If you do not get the same letters back, one of the rules above has been bent.

Common mistakes

Frequent slips and their repairs
WrittenWhat is wrongStandard form
IIIIFour in a row. (Clock faces keep IIII by tradition.)IV
VXV cannot be subtracted.V
ICI may only precede V or X.XCIX
XMX may only precede L or C.CMXC
VVV is never repeated.X
IIXOnly one smaller letter may be subtracted, never two.VIII

Historical writers were looser than these rules. You will find IIII, VIIII and other additive forms on old monuments and documents. The modern standard is a convention for tidiness and teaching, not a law handed down from antiquity.

A short history

The origin of the system is debated, and where scholars disagree we say so. What follows is the broad outline that most accounts share.

  1. Tally and notch

    The oldest layer is counting by marks: one stroke for one, and a different sign for every fifth or tenth stroke. The shapes of I, V and X are often explained as a stroke, an open hand and a crossed pair of tallies.

  2. Signs become letters

    Older signs for fifty, a hundred and a thousand slowly came to resemble the letters L, C and M. Speakers of Latin connected C with centum and M with mille, and the pairing stuck.

  3. A working notation

    Across the Roman world the numerals marked inscriptions, milestones, dates and accounts. Arithmetic itself was usually done on counting boards or with the fingers, and the numerals recorded the result.

  4. Additive and subtractive habits

    Forms like IV and IX occur in antiquity, but so do IIII and VIIII. The strict subtractive style taught today became the norm only gradually, over many centuries.

  5. A long afterlife

    Roman numerals stayed in everyday use in medieval Europe, while Hindu-Arabic digits, with their place value and zero, arrived from the Arabic-speaking world and spread gradually through commerce and scholarship.

  6. The present day

    Today the numerals mark clock faces, cornerstones, book prefaces, chapter lists, outline levels, the numbering of monarchs and popes, film dates and tattoos, wherever a touch of permanence or ceremony is wanted.

Zero, fractions and other absences

Roman numerals have no symbol for zero, because they were never used as a place-value system that needed a placeholder. Medieval scholars working with Roman numerals sometimes wrote the word nulla, or the letter N, when they needed to say that nothing remained. The clock on this site borrows that custom for zero minutes.

Fractions were handled with a separate system, built mostly on twelfths, which is why the Latin word for a twelfth, uncia, survives in our words ounce and inch. This studio sticks to whole numbers from 1 to 3999, and says so plainly when you ask for anything else.

For teachers, designers and tattooists

In the classroom

  • Human numbers. Seven students hold up the seven letters; the class arranges them into a given number and defends the choice.
  • Spot the error. Write six numerals on the board, three of them wrong. Pairs decide which rule each broken one violates, then check with the converter's explanations.
  • Date detective. Bring in photographs of cornerstones, book title pages and film credits. Decode each date and discuss why Roman numerals were chosen.
  • Clock study. Project the clock, hold a time with the controls, and ask the class to say it in numerals before revealing the readout.

At the drawing board

  • Verify before you ink. Convert the date, then convert it back. A permanent mark deserves a double check.
  • Write dates in parts. A day, month and year separated by interpuncts or thin spaces read more clearly than one long string of letters.
  • Choose a legible serif. Heavily decorated faces can turn I, L and V into a puzzle. Test the numeral at the size it will actually appear.
  • Mind accidental words. A few valid numerals read as ordinary words or initials, such as MIX (1009) or DC (600). That may delight you or not.

The inscription maker will give you a clean SVG to start from. It is a sketching aid; leave final spacing and cutting to the person doing the engraving or tattooing.

Practice drill

Direction
Range

Write this number as a Roman numeral

14

Answer, then press Check or the Enter key.
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