% Complete - doesn't seem to calculate properly, what am I missing?

Hi Christine,

You’re not missing anything obvious, this behavior is confusing, and you’re actually seeing how the Project engine under Planner Premium works under the hood.

A key point is that in Project for the web / Planner Premium, % Complete is not a simple “completed effort / total effort” calculation. It follows classic Microsoft Project logic, where % Complete is based on the task’s duration and the time-phased schedule of work, not just the numbers you see in the Effort boxes. 

So in your example:

• You set Completed = 1 hour and Remaining = 1 hour (2 hours total).
• But the task still has a 1-day duration, and internally Project may be scheduling more hours across that day than the 2 hours you typed, or distributing them unevenly over the day.
• When it recalculates, it uses the duration-based % Complete together with the internal schedule, which is why you see something like 6% instead of the 50% you’d intuitively expect for 1 of 2 hours. There are two important behaviors here:

1. Changing Effort affects % Complete
• When you change Completed or Remaining Effort, Project recomputes % Complete based on how much work is scheduled over the task’s duration (time-phased), not just Completed / Total. 
• If the task spans a whole day, and only a small slice of that day has scheduled work so far, the calculated % can look very small.
2. Changing % Complete affects Effort
• When you manually set % Complete to 50%, Project says “OK, halfway through the duration of this task” and then recalculates Completed and Remaining Effort to match that point in the schedule.
• That’s why the hours jump to very different values, it’s trying to keep duration, assignments and effort internally consistent, not just override a single number. 

If you open the Assignments view, you can see the time-phased distribution of work that drives these calculations (though licensing can limit that view, as one of the community replies mentions). 

Because of this, for tutorial content you might want to:

• Pick a simple scenario:
• e.g. 1-day task, 8 hours total effort, single resource, and don’t change duration after work starts.
• Decide on a “driver”:
• Either you always adjust Effort and let Project calculate % Complete,
• Or you only adjust % Complete and let it calculate Effort, but try not to bounce back and forth between both, or the math will look “weird” again. 

If you’re exploring Planner Premium for training material, we have several videos on our MLPro YouTube channel where we walk through Planner Premium and project progress concepts step by step, they might help with additional examples you can reuse in your tutorials

https://www.youtube.com/@MLProPPM

This issue is because % complete is a % complete of the duration, not the effort.   

When you update % complete Planner looks to see how much effort has been scheduled in a time-phase. The easiest way to think of this is hours per day, but it is looking at increments of hours (I haven't yet worked out the smallest increment).

When you update % complete Planner calculates the % complete of the duration and then calculates the total effort that was scheduled within that duration. 

You can only see time phase information in the 'assignments' view (and licensing issues may stop you from seeing this)

For example if I were to update % complete with 20% as per the example below the effort completed would show as 0 hours.

If were to update effort completed with 7.4 the % complete field would calculate to 40%.

If you were to update % complete with 50% that would be time point sometime on Wednesday.

Unfortunately there are more factors at work:

For example there are start and finish times that impact on how Planner schedules effort, so sometimes I am finding that it has scheduled start from 12.00 on the first day and puts all the other hours on the last day. In this case even if you update the effort as say 50% of 37 the % complete may calculate to an unexpected figure, because e.g. only 10 hours have been scheduled by the mid point of the duration.

Unfortunately I do not believe there is a way to edit time although you can see it if you hover above the start and finish fields.

I'm also encountering the same problem with math errors in Planner premium.

I can reproduce the problem by creating a new task, setting the duration to 1 day, setting the total effort to 8 hours, making the task 50% complete, and then changing the duration to 3 days. I can un-break the task by resetting the duration to 1 day, which reduces the total effort to 4.8 hours, and then resetting the total effort to 8h. Then it seems to work normally again.

New task with duration, effort, and partially complete:

Task after changing duration to 3 days. Completed effort and remaining effort were automatically changed.

Task after reducing duration back to 1 day. Total effort, completed effort, and % complete were changed automatically.

The math is now totally broken for the task. Reducing the % complete to 0, correcting the total effort to 8 hours, and increasing the % complete to 50% give a new incorrect value for completed effort.

I am also experiencing a similar issue. I figured the problem on my end was that I had not properly set the effort data but after doing so (painstakingly), the percentages still are not accurate: