Alright then....In order to determine the beats per minute (BPM) of a track what you want to do is time a measure of music with a stopwatch and then calculate the BPM based of the duration of that measure, by the way that is exactly how tap tempo works, however tap tempo tends to be set up to work by timing beats as opposed to bars and thus tends to be less accurate, you can however use it to time bars and simply multiply the resulting BPM thus improving the accuracy........multiplying and dividing is quite an important concept to get your head around especially when dealing with certain software as it allows you to do things like change the grid resolution in programs like ReCycle from 16ths to 8ths etc.
Now just like using tap tempo you will need a sense of rhythm when using a stopwatch and it really helps if you count out loud, just be sure to avoid cutting bars short by hitting stop when you count "4" instead of when you hit the next "1", ideally you want to time bars rather than beats because as you divide you reduce the timing errors you would otherwise get from beat to beat timing, now you might be wondering why, if you can use tap tempo more accurately by multiplying the results would you want to even bother using a stopwatch and calculator, and there are two very good reasons, first the stopwatch gives you a reading of your loop length and second, by understanding the math you can see shit just like Neo looking at the Matrix and seeing past the code.
Now about that red pill.........
Lets say you time 1 bar with your stopwatch and you get a reading of 2.526 seconds, this would be the calculation, 60seconds/2.526seconds(=23.75seconds)x4beats=95 bpm.......
60 seconds is equal to 1 minute as in beats per "minute".
2.526 seconds is the reading from the stopwatch.
(=23.75seconds) you can just ignore that shit.
4 beats is equal to 1 bar........8 beats would be 2 bars and so on.