“Somebody is going to hear this number and take it as your commitment”^[1]

Between two things, number and commitment, we have no issue with the latter. That being said, number states probability between 0% – 100% where in the case of finishing a piece of software, end of week from now could be as low as 0% and–extremely–in 20 years’ time a 100%^[2]. So, instead of coming up with 20 years the whole time–that’s factual but not even funny, usually team committed to a date assigned with less than 100% probability taking into account variations of business factors and risks^[3].

“Ideal days” is the closest number to be marked as commitment along with common mistake of equating them to calendar days (even relative story points can get you almost as close by the way). Ken Rubin found that for 30% of the time, the organization he worked with has no problem with communicating ideal days^[4]. You may belong to the 70%–the majority–dealing with the hard time and choose to either always prolong estimate (a.k.a. inserting guesstimate buffer, contingency days or simply mentioning a number somehow subject to Parkinson Law^[5]) or remedy at execution by overworking to “committed” date.

References

[1] G. Dinwiddie, Software estimation without guessing: Effective Planning in an Imperfect World. Pragmatic Bookshelf, 2019.

[2] P. G. Armour, “Ten unmyths of project estimation,” Communications of the ACM, vol. 45, no. 11, pp. 15–18, Nov. 2002.

[3] M. Cohn, Agile estimating and planning. Pearson Education, 2005.

[4] K. S. Rubin, Essential scrum: A Practical Guide to the Most Popular Agile Process. Addison-Wesley Professional, 2012.

[5] Wikipedia contributors, “Parkinson’s law,” Wikipedia, Jan. 13, 2024. https://en.wikipedia.org/wiki/Parkinson%27s_law