400 = CD
400 is written with just CD.
CD uses subtraction: CD = 400. A smaller symbol before a larger one is subtracted.
| Symbol | I | V | X | L | C | D | M |
|---|---|---|---|---|---|---|---|
| Value | 1 | 5 | 10 | 50 | 100 | 500 | 1,000 |
Need another number? Use the Roman numeral converter (both directions).
| Number | Roman numeral |
|---|---|
| 200 | CC |
| 250 | CCL |
| 300 | CCC |
| 350 | CCCL |
| 450 | CDL |
| 500 | D |
| 550 | DL |
| 600 | DC |