I’ve made a couple minor changes to my page that converts between frequency and pitch. (The page also includes Barks, a psychoacoustic unit of measure.)
If you convert a frequency in Hertz to musical notation, the page used to simply round to the nearest note in the chromatic scale. Now the page will also tell you how sharp or flat the pitch is if it’s not exact.
For example, if you enter 1100 Hz, the page used to report simply “C#6” and now it reports “C#6 – 14 cents” meaning the closest note is C#6, but it’s a little flat, 14/100 of a semitone flat. If you enter 1120 Hz it will report “C#6 + 18 cents” meaning that the note is 18/100 of a semitone sharp.
Octave numbers, such as the 6 in C#6 are explained here.
The other change I made to the page was to add a little eighth note favicon that might show up in a browser tab.
I’ve written several online converters like this: LaTeX to Unicode, wavelength to RGB, etc. See a full list here.