31 = XXXI
31 in Roman numerals is XXXI.
Thirty-one written with the letters X X X I.
31 in words: Thirty-one
Thirty-one in Roman numerals is XXXI. You build it as XXX (30) + I (1), writing the larger part first and reading left to right.
Everything in XXXI is additive here, so you simply add each letter's value together. Numbers like this are a good place to get comfortable before tackling the subtractive forms such as IV and IX.
How 31 breaks down
Reading XXXI from left to right, each group is added together to reach 31:
| Group | Value | Place |
|---|---|---|
| XXX | 30 | tens |
| I | 1 | ones |
| XXXI | 31 | total |
Frequently asked questions
What is 31 in Roman numerals?
31 in Roman numerals is XXXI.
How do you write 31 in words?
31 is written "Thirty-one" in English.
What number comes before XXXI?
The number before XXXI is 30, written XXX in Roman numerals.
What number comes after XXXI?
The number after XXXI is 32, written XXXII in Roman numerals.
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Last updated July 22, 2026. Reviewed for accuracy against the standard rules for Roman numerals.