Determine the tempo of the piece. The tempo is usually indicated by a number at the beginning of the score. The marking may look like MM = 60. If there isn't a number, and there is only a general indication such as Allegro or Andante, you will have to look up the metronome marking for the tempo.
Learn the value of each rhythmic note. A quarter note is the basic unit of time. Each beat in most music is equal to one quarter note. The half note is equal to 2 beats, the eighth note is a half beat and the whole note is worth 4 beats.
Find the total number of times you can play a note in a minute. If the tempo is 72 beats per second then you will have 72 quarter notes or 36 half notes.
Calculate the time of a note. If the tempo is 60 beats per second, then in one minute you can play 60 quarter notes, 30 half notes, 120 eighth notes, or 15 whole notes. So to find the value of a quarter note, divide 60 by the number of notes played in a minute. This will give you the time of a note. This leaves a time of 1 second per quarter note, 2 seconds per half note, 4 seconds per whole note, and half a second for each eighth note.