18 in Roman numerals

XVIII

18 = XVIII

Working: X = 10, V = 5, I = 1, I = 1, I = 1

The number 18 is written as XVIII in Roman numerals.

Roman numerals are built by adding symbol values together from largest to smallest: X = 10, V = 5, I = 1, I = 1, I = 1. Where a smaller symbol appears before a larger one — as in IV for 4 or IX for 9 — it is subtracted rather than added, which keeps the notation short.

Structurally, XVIII is 5 symbols long. It is entirely additive: every symbol adds to the running total, with no smaller symbol standing before a larger one. One symbol repeats three times, which is the maximum the system allows before a subtractive form becomes necessary.

XVIII is five symbols long and one of the more cumbersome numerals below twenty. Compare it to XIX for nineteen, which is shorter despite being a larger number — a good demonstration that numeral length in this system has little to do with magnitude.

Nearby numbers

Number	Roman numeral
11	XI
12	XII
14	XIV
15	XV
16	XVI
19	XIX
20	XX
25	XXV

Try another value

Decimal number (1–3999)

Roman numeral

MMXXIV

Reference

X10

L50

C100

D500

M1000

Frequently asked questions

How do you write 18 in Roman numerals?

18 is written XVIII. It breaks down as X = 10, V = 5, I = 1, I = 1, I = 1.

What are the seven Roman numeral symbols?

I is 1, V is 5, X is 10, L is 50, C is 100, D is 500, and M is 1,000. All Roman numerals are combinations of these seven symbols, and there is no symbol for zero.

For any other value, use the full Roman Numeral Converter on BrainVert.