OmniFocus allows you to assign estimated durations to actions, action groups, and projects. Estimating how long an action will take gives it more definition and helps ensure you don’t take on too much work all at once.
This plug-in calculates the total time, in minutes, of everything you select in the outline.
For example, in the Today perspective, which shows what’s on your list for today, you could select everything in the outline to see how much time it adds up to.
The Estimate Total Time plug-in provides similar functionality.
Read our article on making productive use of estimated durations to get the most out of this feature in OmniFocus.