What does CDXXIV mean?

CDXXIV is the Roman numeral for 424 — 400 + 10 + 10 + 4.

How do you write 424 in Roman numerals?

Take the largest value that fits and repeat until nothing is left: CD (400), then X (10), then X (10), then IV (4). That gives CDXXIV.

424 in Roman numerals

CDXXIV

Number (1–3,999 for numerals)

Roman numeral

424 is written CDXXIV in Roman numerals. That is 4 symbol groups added together, reading left to right from the largest value down.

How it breaks down

CDXXIV = 400 + 10 + 10 + 4 = 424
Group	Value	Subtraction	Running total
CD	400	D − C	400
X	10	—	410
X	10	—	420
IV	4	V − I	424

Why the smaller symbol comes first

CDXXIV uses subtractive notation in 2 places: CD means D minus C, or 400; IV means V minus I, or 4. A smaller symbol placed before a larger one is subtracted from it rather than added, which is why IX is nine and not eleven.

Only six such pairs are valid — IV, IX, XL, XC, CD and CM. That restriction is what makes the notation unambiguous: IIII and IC both look like they should work, but neither is standard, and only one spelling of any number is correct.

The symbols

Symbol	Value	Used here
I	1	yes — 1×
V	5	yes — 1×
X	10	yes — 2×
L	50	no
C	100	yes — 1×
D	500	yes — 1×
M	1,000	no

The same number, other ways

In words: Four hundred twenty-four
Roman numeral: CDXXIV
Symbol count: 6 characters
Binary: 110101000
Hexadecimal: 1A8

The numbers either side

Number	Roman numeral
422	CDXXII
423	CDXXIII
424	CDXXIV ←
425	CDXXV
426	CDXXVI

Common questions

What is 424 in Roman numerals?: 424 is CDXXIV.
What does CDXXIV mean?: CDXXIV is the Roman numeral for 424 — 400 + 10 + 10 + 4.
How do you write 424 in Roman numerals?: Take the largest value that fits and repeat until nothing is left: CD (400), then X (10), then X (10), then IV (4). That gives CDXXIV.

Sources

Calculated on this page — At One Place

How these figures are compiled and checked