Piece of piss.

Wrote a graphing calc program for this ages ago.

Take your frequency and then find out how long each cycle lasts (preferably in the C2-3 region) and multiply that time figure out until you reach between 200-400ms worth, this is your quater bar figure, then put that into this equation

60000/figure = tempo.

this will give you a tempo for an exact number of sinwave cycles in a quater bar...