Body of Knowledge · Glossary
Cone of uncertainty
Estimates are least accurate at the start of work, when least is known, and narrow as reality is discovered. What follows from it: give ranges, cut small slices, de-risk the fuzziest part first, and re-forecast as the cone narrows.
Where the standard develops it
- DE-2Estimation, planning, and honest commitmentsManaging uncertainty rather than chasing accuracy.
Related terms
- Brooks's law
- Adding people to a late software project makes it later, because the existing people must train the new ones and the communication paths multiply.
- Commitment versus estimate
- An estimate is the best forecast.
- Cycle time
- How long work takes from start to done, as measured.
- Planning fallacy
- The systematic tendency to underestimate how long a task will take, even when similar tasks are known to have overrun, because the forecast reasons from the case at hand instead of from the distribution of similar cases.
Cite this definition
Chicago, BibTeX and licence →Engineering Management Academy. (2026). Cone of uncertainty. In Engineering Management Academy Body of Knowledge (Version 3.1, GLO.cone-of-uncertainty). https://www.engineeringmanagement.academy/body-of-knowledge/glossary/cone-of-uncertainty