Pro Tools is actually the most accurate system available when it comes to calculating tempo. Unlike many other programs that require the user to enter a tempo manually, Pro Tools provides a powerful, faster and much more accurate means of defining the song's tempo. By using Pro Tools' Bar|Beat markers you can quickly and automatically find the correct tempo for your song without lengthy experiments or tempo drift.Pro Tools' Bar|Beat markers are based on the highly accurate sample counter inside Pro Tools and guarantee that any MIDI or audio event is placed at a defined sample location even if your song should be 24 hours long. The internal resolution for calculating the tempo between these markers is much greater than the two digits visible in the tempo track or the tempo display, in fact, it's much higher than any number you would want to enter manually!Here's an example that shows that even four decimal digits aren't always enough:At a sample rate of 44100 Hz and a tempo of 100 bpm, 100 beats will take 2646000 samples. At a tempo of 100.0001 bpm, 100 beats will take 2645997 samples. With four decimal digits there is no tempo that will make 100 beats take 2645998 or 2645999 samples; in other words there is an error of three samples. And this is only over one minute duration, imagine what will happen to an hour-long feature or when you try to sync to a two hour movie!Please note while for all practical purposes four decimal places is probably fine, this example clearly shows why we spent a lot of effort to ensure that Pro Tools guarantees 100% accurate positioning of any Bar|Beat marker over any duration in your session. Once you've started using Bar|Beat markers in Pro Tools you may never want to use anything else.