400 in Roman numerals
CD
The number 400 is written CD in Roman numerals.
How CD breaks down
| Symbols | Value |
|---|---|
CD | 400 |
CD | 400 |
This numeral uses the subtractive rule: a smaller symbol placed before a larger one is subtracted from it. Only six such pairs are legal — IV (4), IX (9), XL (40), XC (90), CD (400) and CM (900).
Nearby numbers
| Number | Roman numeral |
|---|---|
| 395 | CCCXCV |
| 396 | CCCXCVI |
| 397 | CCCXCVII |
| 398 | CCCXCVIII |
| 399 | CCCXCIX |
| 400 | CD |
| 401 | CDI |
| 402 | CDII |
| 403 | CDIII |
| 404 | CDIV |
| 405 | CDV |
The seven symbols
I | 1 | C | 100 |
V | 5 | D | 500 |
X | 10 | M | 1,000 |
L | 50 |
400 in other notations
| Roman | CD |
| Binary | 110010000 |
| Hexadecimal | 190 |
| Octal | 620 |
| Written out | four hundred |
Writing it by hand
Work down through the symbol values, taking as many of each as will fit before moving to the next. For 400:
CD = 400 remaining: 0The result reads CD — 2 characters, against 3 digits in Arabic numerals.
Frequently asked questions
What is 400 in Roman numerals?
CD
How do you read CD?
Work left to right, adding each symbol — except where a smaller symbol precedes a larger one, in which case it is subtracted. CD is 400.
How do you write 400 in words?
four hundred.
Why is there no zero?
Roman numerals have no symbol for zero. The concept reached Europe only with Hindu-Arabic numerals, centuries after the system was in use — which is a large part of why it was eventually replaced for arithmetic.