This one has bothered me for a long while.
I like to do estimates thinking on how much time a certain task will take (I'm in TI business), so, let's say, it takes 12 hours to build a program.
Now, let's say I tell Project that my beginning date is today. If I allocate one resource to this task, it means that the task will last 1,5 days, implying that it will end tomorrow.
But right now, that is not what it's doing. I say that the task will take 1 hour, and when I add a resource to it, it allocate the resource at [13%] basis, which means that the duration is still fixed… project is trying to make the task last for a day.
I have, on many occasions, accomplished this. What I do is build a plan based on these rough estimates for effort, then I allocate tasks to resources. Times conflict, so I level resources and then Project magically tells me how long, in days, will it take. But every time I have to start estimating again, I end up having trouble on how to make project work like that.
Best Answer
You may be running into what has confused me for a long time. You are probably entering your estimates into the "duration" column. Whenever you do something to the task, like setting a start and end date it may change the duration.
By default, MS Project does not show you the "work" column. Make it visible and put your estimates in there, where they will not change, even though duration changes.