Unit and number converters
Converters for number systems, codes and units, from Roman numerals and Caesar shifts to Morse code and metric-imperial measurements.
Free · run in your browser · nothing uploaded
Numbers
Codes and ciphers
Units and measurements
Audio
About these tools
Unit conversion looks trivial until precision or an unfamiliar unit is involved — cooking measures that differ between countries, imperial and metric mixtures on the same drawing, or number systems that need converting rather than approximating.
These pages convert exactly and show enough of the working that you can check them. Everything is calculated in your browser as you type, with no rounding applied until the display step.
Questions people ask
Why does the Roman numeral converter stop at 3,999?
Standard Roman numerals have no symbol above M (1,000) and do not repeat a symbol more than three times, so MMMCMXCIX (3,999) is the largest number they can write. Larger values historically used a bar over a numeral to multiply it by 1,000, which is not a standard notation today.
Is a Caesar cipher secure?
No. There are only 25 possible shifts, and the Caesar cipher tool can try all of them at once to crack a message. Use it for puzzles and teaching; for anything private, use Text encryption, which applies AES-256 with a password.