Roman Numeral Converter
Convert numbers to Roman numerals and Roman numerals to numbers, from 1 to 3999.
Runs in your browser Your input never leaves your device.
Reference table
| I | 1 | V | 5 | X | 10 | L | 50 |
|---|---|---|---|---|---|---|---|
| C | 100 | D | 500 | M | 1000 | ||
| IV | 4 | IX | 9 | XL | 40 | XC | 90 |
| CD | 400 | CM | 900 |
Type in either box and the other updates. Standard Roman numerals have no zero and stop at 3999 (MMMCMXCIX); larger numbers used a bar over the letters, which this tool does not write. Runs in your browser.
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About this tool
Type a number from 1 to 3999 and see it as a Roman numeral, or type a Roman numeral and see the number; either box updates the other as you type. The letters are I (1), V (5), X (10), L (50), C (100), D (500) and M (1000). A smaller letter before a larger one is subtracted, so IV is 4 and CM is 900, and only I, X and C can be subtracted. Numerals written the old additive way, such as IIII for 4 or VIIII for 9, are understood and the tool tells you the standard spelling (IV and IX). Invalid combinations such as VX, IC or MMMM are rejected with the reason. Standard Roman numerals have no zero and stop at 3999 (MMMCMXCIX); larger numbers were written with a bar over the letters, which this tool does not produce. The reference table shows the basic values. Everything runs in your browser.
How to use it
- Type a number in the first box, or a Roman numeral in the second.
- Read the converted value in the other box.
- If the numeral is not the standard spelling, read the note under the boxes.
- Press Copy numeral to copy the Roman numeral.
Common problems
- Why is IIII accepted but not shown as the answer?
- Clock faces and some old texts use IIII for 4, so it is understood, but the standard form is IV. The tool tells you the usual spelling.
- Why does it stop at 3999?
- Without the bar notation, a letter cannot repeat more than three times, so the largest standard numeral is MMMCMXCIX (3999).
- Why is zero not allowed?
- The Romans had no symbol for zero. Use the word nulla if you need to write it.