Number
40 in Roman numerals
40 is written XL
Type any other number or numeral below to convert it.
Above 3,999? Type the barred part in brackets, e.g. (IV)CC = 4,200.
How XL is built
Roman numerals are written one decimal place at a time, largest first.
- XLtens · 4X before L means 50 − 10 = 40. This saves writing XXXX.
The pair XL uses subtraction: a smaller letter before a larger one is taken away from it. Only six pairs work this way: IV, IX, XL, XC, CD and CM. More on subtraction
Mistakes to avoid
- Not XXXX (4 letters). That adds everything up without subtraction. The Romans sometimes wrote numbers this way, and clocks still show 4 as IIII, but today XL (2 letters) is the standard.
- There's no letter for zero. The zero is simply left out, which is why 40 has 1 part, not 2.
About the number 40
- 40 is even and can be split into prime factors: 2 × 2 × 2 × 5, or in Roman numerals II × II × II × V.
- XL has 2 letters. 969 of the numbers up to 1,000 have longer numerals.
Counting from 31 to 40
| Number | Roman numeral |
|---|---|
| 31 | XXXI |
| 32 | XXXII |
| 33 | XXXIII |
| 34 | XXXIV |
| 35 | XXXV |
| 36 | XXXVI |
| 37 | XXXVII |
| 38 | XXXVIII |
| 39 | XXXIX |
| 40 | XL |