Roman Numeral Converter
Convert a number into Roman numerals, or a Roman numeral back into a number. Results update live as you type — nothing is uploaded, everything runs in your browser.
Your input stays in your browser — nothing is sent anywhere.
How to use the Roman numeral converter
Type a number from 1 to 3999 in the first box to see its Roman numeral, or type a Roman numeral in the second box to read off its value. Both directions update instantly as you type — there is no button to press and nothing leaves your device.
The seven Roman letters and their values are I = 1, V = 5, X = 10, L = 50, C = 100, D = 500 and M = 1000. You read them left to right, adding the values, except where a smaller letter comes before a larger one — then you subtract. That subtractive rule gives the six special pairs: IV = 4, IX = 9, XL = 40, XC = 90, CD = 400 and CM = 900.
So a year like 1994 becomes MCMXCIV: M (1000) + CM (900) + XC (90) + IV (4). The converter only accepts well-formed, standard numerals, so it will flag mistakes like IIII or IC.
Everything runs in your browser — the numbers and numerals you type are never uploaded.
Common questions
Why does it stop at 3999? Standard Roman numerals only use the letters up to M (1000), so the largest value you can write without an overbar is MMMCMXCIX, which is 3999. Larger numbers historically used a bar over a letter to multiply it by 1000.
Can I use lowercase letters? Yes. Type in any case — the tool reads mmxxiv and MMXXIV the same way and shows the result in standard uppercase.
What counts as a valid numeral? Only canonical numerals. A letter never repeats four times, and only I, X and C can be used to subtract (before the next one or two larger letters). Anything else is rejected as invalid.
Is anything saved or uploaded? No. The tool is fully client-side — your input never leaves your browser and nothing is stored.