Roman Numeral Converter

Type a year, a chapter number or a numeral and this converts between ordinary numbers and Roman numerals from 1 to 3999. It also checks the form: IIII is flagged and the standard IV suggested, so it doubles as a quick proofreader for monuments, film credits and clock faces.

How to use it

1. Type a number or a Roman numeral.
2. The tool works out which one you've given it.
3. Read the conversion in the result.
4. Copy it into your work.

When it helps

• Writing the year on a plaque, cornerstone or film title.
• Numbering chapters, appendices and outlines.
• Reading old documents and clock faces.
• Checking schoolwork.

Good to know

• Roman numerals have no zero, and the standard system stops at 3999.
• A smaller numeral before a bigger one subtracts: IX is nine, XL is forty.
• Some clock faces deliberately use IIII, but standard writing uses IV, and that's what this tool expects.

How Roman numerals work

Roman numerals use seven letters: I (1), V (5), X (10), L (50), C (100), D (500) and M (1,000). Letters are written largest to smallest and added together, so VIII is 8. When a smaller one comes before a larger one, it's subtracted: IV is 4 and IX is 9, XL 40, XC 90, CD 400 and CM 900.

The standard rules say you can repeat a symbol up to three times, so III is 3 but IIII isn't standard, and you can only subtract powers of ten, so IL for 49 is wrong and XLIX is right. The tool checks those rules when you enter a numeral.

Worked example: MCMXCIV

Read it in chunks: M is 1,000, CM is 900, XC is 90, IV is 4. Add them up: 1,000 plus 900 plus 90 plus 4 is 1,994. Going the other way, 2026 splits into 2,000, 20 and 6, giving MM, XX and VI, so MMXXVI.

Dates are the most common use. Film copyright notices, building cornerstones and Super Bowl numbers all use Roman numerals, and the tool saves you from counting letters carefully.

Where you'll still see them

Clock faces, book prefaces, outlines, monarchs and popes (Elizabeth II, Pope Leo XIV), and event series such as the Olympics' older editions all use them. Some clocks show 4 as IIII, following a tradition that goes back centuries, which is a fun exception to the usual rule.

Roman numerals have no zero and no easy way to write fractions or very large numbers, so mathematics moved on to the Hindu-Arabic system we use today.

Limits

The tool handles 1 to 3,999, the range that standard numerals can express without extra symbols. Larger numbers historically used a bar above a numeral to multiply it by 1,000, but that isn't widely supported in text.

If you need numbers for a design, such as a clock or a tattoo, double-check the result with the original rules. A single wrong letter changes the meaning.

Questions