Roman Numeral Converter
Convert Roman numerals to Arabic numbers and back — from 1 to 3999. Includes a full reference table, strict validation and recent conversion history.
Roman numerals table 1–1000
About the Roman numeral converter
The converter works both ways: type MCMXCIX and get 1999, type 2024 and get MMXXIV. Conversion happens automatically while you type, the Swap button changes direction, and history keeps the most recent results one click away.
The algorithm supports the range 1–3999 — the upper limit of standard Roman numerals without the overline notation for thousands. It uses subtractive notation (IV=4, IX=9, XL=40, XC=90, CD=400, CM=900) and validates repetition rules: IIII is rejected because the canonical form is IV.
All conversions run locally in your browser without uploading anything to a server. Below the input you will find a quick reference table 1–1000 for checking the spelling of years, chapter numbers and centuries.
What the converter does
Two-way conversion
From Roman to Arabic and back — automatically as you type, no Calculate button. Just start typing.
Strict validation
If you type IIII, IC or VV — you see an error. Only canonical forms following subtractive notation rules are accepted.
Reference table and history
A full 1–1000 table for quick lookups and a history of the last eight conversions — click to restore any of them.
FAQ about Roman numerals
How are Roman numerals written — the basic rules
Seven symbols: I=1, V=5, X=10, L=50, C=100, D=500, M=1000. A smaller symbol before a larger one is subtracted (IV=4, IX=9, XL=40, XC=90, CD=400, CM=900); after a larger one it is added (VI=6, XI=11). A symbol may repeat at most three times in a row (III=3, XXX=30, CCC=300), while V, L and D never repeat.
Why is there no zero in Roman numerals?
Roman numerals are a non-positional system that emerged long before the Hindu-Arabic notation with zero. Romans did not need a “nothing” symbol for counting on an abacus, so there is no dedicated digit for zero. The concept of emptiness was expressed by the word “nulla”, but zero as a full-fledged digit only reached Europe in the 12th–13th centuries together with Arabic numerals.
Why is the maximum 3999 and not more?
In the classic notation without special marks (overlines, frames) you can use no more than three M characters in a row (3000). The maximum is therefore MMMCMXCIX = 3999. Numbers from 4000 upwards require a special notation with an overline (V with a bar = 5000), which modern converters generally avoid because outside of historical contexts it is rarely needed.
Are Roman numerals taught at school?
Yes, Roman numerals are introduced in primary school — usually in years 3–4 — for centuries and ordinal numbers. In secondary school they appear in history, literature (chapter numbering), physics and technical drawing. The converter is handy for checking homework and formatting essays.
Is the converter safe — does my data stay private?
Yes, the conversion happens entirely in your browser in JavaScript. Numbers are never sent to a server, and history is stored only in your browser’s local storage on this device. You can clear it any time with the Clear button in the History block.