18 in Roman numerals is XVIII, built from X + V + III (X = 10, V = 5, III = 3), which add up to 18.
How 18 is written in Roman numerals
The number 18 is written XVIII in Roman numerals. Roman numerals use seven letters — I (1), V (5), X (10), L (50), C (100), D (500) and M (1000) — combined from largest to smallest, with subtractive pairs such as IV (4) and IX (9). Need another number? Use the Roman numeral converter or see the 1–100 chart.
Building XVIII step by step — take the largest value that fits, write its symbol, subtract, repeat.
| Write | Value | Remaining before | Remaining after |
|---|
| X | 10 | 18 | 8 |
| V | 5 | 8 | 3 |
| I | 1 | 3 | 2 |
| I | 1 | 2 | 1 |
| I | 1 | 1 | 0 |
Where you see XVIII
Regnal and papal names use it the same way — a 18th ruler of a name is styled XVIII, as in Louis XVIII or Pope John XVIII. The 18th Super Bowl was Super Bowl XVIII; the NFL has used Roman numerals for every edition except Super Bowl 50.
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Frequently Asked Questions
What is 18 in Roman numerals?
18 in Roman numerals is XVIII. Reading it left to right gives X (10) + V (5) + I (1) + I (1) + I (1) = 18. The number below it, 17, is written XVII, and the number above it, 19, is written XIX.
How do you write 18 in Roman numerals?
Write 18 as XVIII, combining X (10) + V (5) + I (1) + I (1) + I (1). Roman numerals are built by taking the largest value that still fits, writing its symbol and subtracting it, which reduces 18 in 5 steps: X leaves 8, V leaves 3, I leaves 2, I leaves 1, I leaves 0. Every symbol keeps the same value wherever it stands, so the order is fixed and XVIII is the only standard spelling of 18.
What are the Roman numerals either side of 18?
Either side of 18 the Roman numerals are XVII for 17 and XIX for 19, with XVIII between them. Those three numerals are 4, 5 and 3 letters long, so the length changes as you count. Roman numerals have no digit positions, so each step can rewrite the numeral rather than bumping a single digit.
What is 18 times ten in Roman numerals?
18 times ten is 180, which is CLXXX in Roman numerals, not XVIII with a letter added on the end. Roman numerals have no place value, so multiplying by ten respells the whole numeral instead of shifting digits along. Compare XVIII for 18 with CLXXX for 180.