Roman Numerals Converter

Convert between Roman numerals and decimal numbers

Decimal Number (1-3999)

How to Use This Roman Numerals Converter

Choose conversion direction

Select whether you want to convert a decimal number to Roman numerals or convert Roman numerals back to decimal.

Enter your value

Type a decimal number between 1 and 3999, or enter Roman numerals like MMXXIV for 2024.

Get your result

Click Convert to see the converted value instantly. No sign-up required, results display right on the page.

Roman Numeral Reference Table

Roman Numeral	Decimal Value	Roman Numeral	Decimal Value
I	1	L	50
V	5	C	100
X	10	D	500
M	1000	MM	2000
MMM	3000	MMMCMXCIX	3999

Note: Standard Roman numerals only support values from 1 to 3999. Larger numbers require special notation.

Understanding Roman Numerals

Roman numerals use seven letters from the Latin alphabet to represent values: I (1), V (5), X (10), L (50), C (100), D (500), and M (1000). Unlike our decimal system, Roman numerals combine these letters using addition and subtraction rules.

The subtractive principle is key to reading Roman numerals correctly. When a smaller value appears before a larger one, you subtract it. IV means 4 (5 minus 1), not 6. Similarly, IX is 9, XL is 40, and CM is 900. This rule prevents four identical letters in a row — you write IV instead of IIII.

Roman numerals still appear in everyday life: movie copyright dates, clock faces, book chapter numbers, Super Bowl numbering, and monarch names like Queen Elizabeth II. Understanding the system helps you decode these at a glance.

Historical note: The Romans themselves didn't always follow strict rules. You might see IIII on clock faces instead of IV — this is called the "watchmaker's four" and was used for visual balance.

Tips for Reading and Writing Roman Numerals

Break it into groups

Read Roman numerals from left to right, grouping subtractive pairs first. For MMXXIV: MM (2000) + XX (20) + IV (4) = 2024. This chunking approach makes large numbers manageable.

Know the subtractive combinations

Only six subtractive combinations exist: IV (4), IX (9), XL (40), XC (90), CD (400), and CM (900). Memorizing these makes conversion much faster.

Watch for invalid forms

You cannot repeat I, X, C, or M more than three times in a row. V, L, and D never repeat. IV is valid; IIII is not standard. VX is invalid — you cannot subtract V from anything.

Use this converter for verification

When learning Roman numerals, convert back and forth to check your work. This tool handles all valid combinations from 1 to 3999 instantly.

Frequently Asked Questions

Why does Roman numerals stop at 3999?

Standard Roman numeral notation has no symbol for 5000 or 10000. The Romans used special marks (vinculum bars) over letters to multiply by 1000, but these aren't supported in plain text. Our converter handles 1-3999, which covers most practical uses.

Is IIII or IV correct for 4?

IV is the standard subtractive form. IIII appears on some clock faces for visual symmetry — it balances VIII on the opposite side. Both are readable, but IV follows the formal rules.

How do you write zero in Roman numerals?

You don't. The Romans had no concept of zero as a number. Their system was for counting and measuring, not abstract mathematics. Medieval scholars later used "N" (from nulla) for zero in some contexts.

Can Roman numerals have lowercase letters?

Yes, lowercase roman numerals exist (i, v, x, l, c, d, m) and follow the same rules. They're often used for page numbers, outlines, and introductory sections. This converter accepts both cases.

What's the longest Roman numeral under 4000?

3888 (MMMDCCCLXXXVIII) uses 15 characters — the maximum for standard notation. Numbers with many 8s require the most letters since 8 is VIII (four characters).

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