What does CDXXVIII mean?

CDXXVIII is the Roman numeral for 428 — 400 + 10 + 10 + 5 + 1 + 1 + 1.

How do you write 428 in Roman numerals?

Take the largest value that fits and repeat until nothing is left: CD (400), then X (10), then X (10), then V (5), then I (1), then I (1), then I (1). That gives CDXXVIII.

428 in Roman numerals

CDXXVIII

Number (1–3,999 for numerals)

Roman numeral

428 is written CDXXVIII in Roman numerals. That is 7 symbol groups added together, reading left to right from the largest value down.

How it breaks down

CDXXVIII = 400 + 10 + 10 + 5 + 1 + 1 + 1 = 428
Group	Value	Subtraction	Running total
CD	400	D − C	400
X	10	—	410
X	10	—	420
V	5	—	425
I	1	—	426
I	1	—	427
I	1	—	428

Why the smaller symbol comes first

CDXXVIII uses subtractive notation in one place: CD means D minus C, or 400. 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 — 3×
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-eight
Roman numeral: CDXXVIII
Symbol count: 8 characters
Binary: 110101100
Hexadecimal: 1AC

The numbers either side

Number	Roman numeral
426	CDXXVI
427	CDXXVII
428	CDXXVIII ←
429	CDXXIX
430	CDXXX

Common questions

What is 428 in Roman numerals?: 428 is CDXXVIII.
What does CDXXVIII mean?: CDXXVIII is the Roman numeral for 428 — 400 + 10 + 10 + 5 + 1 + 1 + 1.
How do you write 428 in Roman numerals?: Take the largest value that fits and repeat until nothing is left: CD (400), then X (10), then X (10), then V (5), then I (1), then I (1), then I (1). That gives CDXXVIII.

Sources

Calculated on this page — At One Place

How these figures are compiled and checked