# The 80%/20% rule of project scheduling

The first 80% of the tasks take 80% of the time.
The final 20% of the tasks take the remaining 80% of the time.

Sadly, this is true more than we want to believe.

Don’t you mean the first 80% takes 20% of the time.

Also, this was one of the first lesson I learned my first semester as a mechanical engineering major. It could not be more true. The closer to finishing a project you get, the more problems (and more difficult problems) you run in to.

Maybe it means that we need 160% of the time we actually get, but I guess “the first 80% takes 20% of the time” is more inline with other 8020 rules.

Sadly, this is true more than the rest of us want to believe either.

If one is following Karthik’s Golden Rules, you are likely to be correct.

If one is breaking Karthik’s Golden Rules, what garyk wrote might be generous.

I’ve also heard it expressed as the 90-90 rule: the first 90% takes 90% of the time, and the last 10% takes the other 90% of the time.

That would be the pessimist’s version…

Right now its seeming like the 99/1 rule…