How can I better estimate the real scale of a project?

Are there techniques to help reduce the error of estimating the hours required to do a project? ... some manner of formula with numerous terms such as the Drake equation?

The Drake equation is a probabilistic argument used to estimate the number of active, communicative extraterrestrial civilizations in the Milky Way galaxy.

The Drake equation is:

N = R ⋅ fp ⋅ ne ⋅ fl ⋅ fi ⋅ fc ⋅ L


N = the number of civilizations in our galaxy with which communication might be possible (i.e. which are on our current past light cone);


R = the average rate of star formation in our galaxy
fp = the fraction of those stars that have planets
ne = the average number of planets that can potentially support life per star that has planets
fl = the fraction of planets that could support life that actually develop life at some point
fi = the fraction of planets with life that actually go on to develop intelligent life (civilizations)
fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space
L = the length of time for which such civilizations release detectable signals into space

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    Properly assessing the tasks and subtasks, knowing the source of variance and their range. And give bigger ranges, experience also helps.
    – Al rl
    Commented Oct 12, 2020 at 23:40
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    Ummm... what have your Google and searches yielded so far? Somehow I suspect this may be off-topic here, asking for ways to estimate projects is basically asking us to do your work for you (besides I guess ways to do that are many and all should be documented in PM books and resources)
    – DarkCygnus
    Commented Oct 12, 2020 at 23:40
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    @JoeStrazzere I would even bet it is very likely it's already been asked over there... thanks for the link
    – DarkCygnus
    Commented Oct 12, 2020 at 23:56
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    Study of estimation is a whole discipline by itself. Asking how to do it better is like asking how to do software development better - it depends where you are at now, and there are many things you can do. If there is something in the 12 books you have read you don't understand ask about that. And I don't think "surmise" is the word you mean here. Commented Oct 13, 2020 at 3:10
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    The Drake equation us actually very like the various formulae for software estimation in that it is a fairly obvious calculation based on numbers that we have no real way of knowing the value of. Commented Oct 13, 2020 at 3:14

2 Answers 2


Are there techniques to help reduce the error of estimating the hours required to do a project?

Yes, there are, but none of them will actually guarantee you anything. The main activity of a project manager is planing and tracking. The tracking part is the part where you verify if the previous estimates still hold and, if not, change them.

Beyond this, there is the vast science of project management. The resources are countless form where to learn. Your job is one of the best resources of lessons. If you cannot learn from your own mistakes, then you cannot really learn from other people's mistakes either.

  • "If you cannot learn from your own mistakes, then you cannot really learn from other people's mistakes either." It seems to be anyone can as making mistakes have having insights about them aren't related. Commented Oct 13, 2020 at 21:05
  • @RandyZeitman: you are mostly right. But we do not live long enough to learn only from our own mistakes :)
    – virolino
    Commented Jan 11, 2021 at 5:55

No, you can not. Read up on agile development and SCRUM - the whole core concept of SCRUM is an acceptance that hour based estimates over a longer timeframe are bunk, never right and not worth doing. Hence a ton of methods around delivering a minimum valuable product with a lot of "nice to have" features in case there is time, and not doing any hourly estimates for more than a single sprint (1-2 weeks max) because - any longer term planning just does not work. Never did, never has been really done.

  • Citation needed for Scrum being against long term planning. What do you think story points are for?
    – meriton
    Commented Jan 10, 2021 at 19:57
  • Ah, the context is HOURS - story points are a vague measurement of complexity. The OP is explicitly talking about "error of estimating the hours required to do a project". Scrum avoids that by going EXTREMELY vague with story points AND accepts them being off and NOT representing hours, so there are no hours there. As the whole question is about hours, I assumed a comment would - read the context.
    – TomTom
    Commented Jan 10, 2021 at 19:59
  • The OP is talking about some idiot (no, someone similar) I had once as manager - who came to us with a MS Project project assigning every programmer to exact tasks for the next YEAR (!) in 15 minute (!) intervals. He came to me because we never kept to his project - and his time estimates.
    – TomTom
    Commented Jan 10, 2021 at 20:00
  • That makes sense, thanks for the clarification. (I commented because the title of the question asks about "estimating scale", not just "estimating hours" - and read in that context, your answer might be understood to mean that SCRUM says estimation is never worth doing ... which would be wrong, as we both agree)
    – meriton
    Commented Jan 10, 2021 at 20:12

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