Roman Numeral Converter

Type in a number from 1 to 3999 to get its Roman numeral, or a Roman numeral to get the number back — either direction shows a place-value breakdown of exactly how the result was built.

For personal planning and general reference — verify important results when needed.

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Converter

1-3999

Enter a number between 1 and 3999

Enter a number or Roman numeral, then click Convert to see the result with detailed breakdown, charts, and analysis.

The seven symbols everything is built from

Roman numerals use just seven letters, each standing for a fixed value. Every Roman numeral, no matter how long, is some combination of these seven repeated and arranged according to two rules.

Roman numeral symbol values
Symbol Value
I1
V5
X10
L50
C100
D500
M1,000

Additive and subtractive notation

Most of the time, symbols simply add together from left to right: VI is 5 + 1 = 6, and XII is 10 + 1 + 1 = 12. The exception is a short list of subtractive pairs, where a smaller symbol placed immediately before a larger one means subtract instead of add — this is how the numerals avoid ever repeating a symbol more than three times in a row.

Roman numeral subtractive pairs
Pair Value
IV4 (5 − 1)
IX9 (10 − 1)
XL40 (50 − 10)
XC90 (100 − 10)
CD400 (500 − 100)
CM900 (1,000 − 100)

Converting a number by hand

The trick is to work from the largest value down, peeling off one chunk at a time. Take 2024:

2024 = 1000 + 1000 + 10 + 10 + 4

= M + M + X + X + IV

= MMXXIV

Going the other direction works by scanning left to right and comparing each symbol to the one after it: if a symbol is smaller than the next one, subtract it; otherwise add it. MMXXIV breaks down as M(+1000) M(+1000) X(+10) X(+10) I(smaller than V, so −1) V(+5), totaling 2024 again.

Where Roman numerals still show up today

Clock and watch faces use them for a classic look — often with IIII instead of IV so the four-letter block visually balances VIII on the opposite side. Movie sequels, book chapters, outlines, and the names of monarchs and popes (Elizabeth II, Super Bowl LVIII) all lean on Roman numerals for a formal or traditional feel rather than practicality. Copyright years in film credits are a well-known example too — MCMXCIX for 1999, spelled out the same additive-and-subtractive way as any other year.

Converting other kinds of numbers and units

For everyday unit conversions rather than numeral systems — length, weight, temperature, and more — the conversion calculator covers those in one place.

Frequently Asked Questions

How do Roman numerals work?

Roman numerals combine letters — I, V, X, L, C, D, M — with additive and subtractive rules. IV = 4 (5 − 1), while VI = 6 (5 + 1).

What are the basic Roman numeral values?

I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A smaller value before a larger one subtracts; after, it adds.

What numbers cannot be written in Roman numerals?

Classic Roman numerals have no zero and no standard fractions. Very large numbers use vinculum (overbar) extensions in some notations.

Where are Roman numerals still used?

Clock faces, book chapters, movie sequel titles, and some legal or ceremonial numbering still use Roman numerals for tradition or style.

How do I use this Roman numeral converter?

Enter an Arabic number or a Roman numeral string, then click Convert. The equivalent value appears with validation for invalid sequences.

Why does the converter stop at 3999?

Standard Roman numerals never repeat a letter more than three times in a row, and there is no single symbol for 5,000 or higher in everyday notation. 3999 (MMMCMXCIX) is the largest number those seven letters can represent without extending the system.

Why is 4 written as IV instead of IIII?

IIII is actually how Romans often wrote 4 historically, and clock faces still use it for visual symmetry with VIII. Modern standard notation prefers the subtractive form IV: one smaller symbol placed before a larger one means subtract it, which keeps numerals shorter and avoids repeating a letter four times.

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