rncbc.org a.k.a. Rui Nuno Capela

The calculation seems perfectly correct :) Where's the catch?

Let me explain: Dividing the time range interval of 7.684 seconds by 24 beats gives you a duration of 0.32 seconds for each beat, which in turn is to say that's a rate of 60 / 0.32 = 187.4 beats per minute, thus the calculated tempo.

What should be the tempo you expected? Look again, time signature (6/8) doesn't play a thing in this calculation ;) nb. a beat is always equivalent to a standard quarter-note duration (1/4) aka. crotchet, seminima, etc.

Seeya