So on the other hand, then why do we estimate (with extremely limited information) that this project will take 7 months for 8 developers, and exactly TO THE DAY, we deliver the final projects 7 months later and the client is happy?<p>AKA you can&#x27;t estimate pieces, but you can still say this will be done in 3 months, and then you manage scope etc. so it&#x27;s done in 3 months.<p>Or: you can&#x27;t estimate how long this will take, but you can set a &quot;how long&quot; given flexibility in the &quot;this&quot;.