Script Debugger automatically times your script as it runs. The timings accumulate as the script runs, and the total cumulative results can be viewed afterwards. This feature is especially useful during development when you’re trying to make your script as fast and efficient as possible.

To learn how long your script took to run, you don’t need to do anything special. Just run the script. The result drawer displays the timings, at the bottom of the drawer:

A typical timing might be something like this:

Duration: 1.12s, AppleScript: 0.03s, AppleEvents: 1.09s (92)

The times displayed consist of the total duration, followed by a breakdown into time spent within the script itself and time spent sending Apple events (and waiting for the replies). The two latter times will sum to the former. The number in parentheses is the number of Apple events sent.

You can also get a handle on what Apple events are being sent by using the Apple Event Log.