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 for everything you select in the outline and identifies any selected items without an estimated duration.
For example, in the Today perspective, which shows the actions you’d like to complete today, you could select everything in the outline to see how much time they’ll take and spot any that are missing a duration.
Read our article on making productive use of estimated durations to get the most out of this feature in OmniFocus.