What Does X Mean in Roman Numerals?
X is ten, the anchor of the tens place the way I anchors the units. It is a clean crossed pair of strokes, and it is the hinge for everything from XI in the low tens up to the high nineties.
Where X comes from
One common account reads the X as two V shapes joined point to point, five and five making ten. Another traces it to a crossed tally, the tenth notch struck through to mark a group. Either way it settles into the tidy cross that made it easy to carve.
How X behaves
- X repeats up to three times: X, XX, XXX for ten, twenty and thirty. Forty is XL, not XXXX.
- X is a subtracting symbol. Before L or C it is taken away, giving XL (40) and XC (90).
- X is only subtracted from the next two values up, L and C. It is never placed before D or M.
X in action
The same symbol behaves differently depending on what sits beside it. These worked examples show X added, and where it applies, subtracted.
| Number | Numeral | What X is doing |
|---|---|---|
| 30 | XXX | XXX is three tens added together. |
| 40 | XL | XL is ten before fifty: the X is subtracted. |
| 90 | XC | XC is ten before a hundred, the other place the X subtracts. |
| 24 | XXIV | XXIV is twenty, then four, a mix of added and subtracted tens and ones. |
Try it in the converter
Type any number to see where X lands inside its numeral, or read a numeral back to a number.
10 is written X in Roman numerals.
Frequently asked questions
What does X mean in Roman numerals?
X means ten. It anchors the tens place and is one of the three symbols that can be subtracted.
How do you write forty and ninety with X?
Forty is XL, ten placed before fifty, and ninety is XC, ten before a hundred. In both the X is subtracted rather than repeated.
How many times can X repeat?
Up to three: X, XX and XXX. Forty switches to the subtractive XL, mirroring how four becomes IV in the units.