A client asked us last month, reasonably, why our proposal said "seven to eleven weeks" instead of a date. The honest answer is that the date would have been fiction with better formatting.
A single number hides the assumption
Every estimate rests on assumptions: that the third-party API behaves as documented, that the client's existing data is as clean as described, that nobody adds scope mid-sprint. A single number bakes those assumptions in silently. A range makes the width of our uncertainty visible, which is more honest and, it turns out, more useful.
The range is not padding
We do not widen a range to protect ourselves from blame. It comes from a specific method: we estimate the parts of the work we understand well tightly, the parts we do not understand yet widely, and the total is the sum, not a guess dressed up as one. If a range looks uncomfortably wide, that is a signal to spend a day narrowing the unknown before quoting at all, not a reason to round it down.
What we tell clients about the width
- A tight range means the work resembles something we have built before.
- A wide range usually points at one specific unknown — an integration we haven't tested, a data migration of unknown quality — and we name it rather than hide it in the number.
- A range that keeps growing during discovery is a reason to stop and re-scope, not a reason to keep discovering.
The date at the end still moves
Even a careful range assumes stable scope. The estimate is revisited whenever a client adds something significant, in writing, with the effect on the range stated at the same time as the request is agreed — not three weeks later when the deadline is missed.
A precise-looking estimate is not more useful than an honest range. It is just more convincing until the date arrives.
The trade we made
Some prospective clients want a number for their own board meeting and go elsewhere for it. We have decided that is an acceptable loss. The projects we take on this way run to their range far more often than the ones we used to quote to a date, and the conversation at week six is about progress rather than about who said what.