 Musical interval

 
This calc gives the musical interval between two notes described by their frequencies. This is done by a simple exponential relationship, assuming that there are 12 semitones for each doubling of frequency.
 
Note that this calc uses equal temperament (i.e. it assumes that an octave divides exactly into 12 semitones). This is the way that the majority of modern music is played. For this reason, there may be some small differences to expectation e.g. a perfect 2:3 ratio of frequencies does not give an exact perfect 5th (7 semitones). Another calc can be used to make the reverse calculation.  