Guide

6/8 and 3/4 in these tools

Both meters can feel like groups of three, so it is easy to mix them up. The tools on this site keep one rule and use it everywhere: duration and the metronome count beats you would conduct.

In 3/4 there are three quarter-note beats in the bar. At 120 BPM, one bar lasts 3 × (60 / 120) = 1.5 seconds. Eight bars last 12 seconds.

In 6/8 there are two dotted-quarter beats in the bar. At 120 BPM, one bar lasts 2 × (60 / 120) = 1 second. Eight bars last 8 seconds. The written bar still contains six eighth notes, but BPM is the dotted-quarter pulse, not the eighth note.

That choice matches common metronome markings for compound duple time. If you instead counted six eighths as six beats, the same 120 would mean a much faster written eighth and a longer bar at that number. These pages do not switch rules in the middle of a session.

The metronome can still click eighths under the 6/8 pulse: three lighter clicks on each dotted-quarter beat, with the accent on beat one. Duration tools do not change when you turn subdivisions on. They still use two beats per 6/8 bar.

Try the same 8 bars at 100 BPM on the song length calculator: 3/4 gives 14.4 seconds; 6/8 gives 9.6 seconds. If those two numbers ever matched, the rule would have been broken.