Story points are relative, by falling into the trap of converting them into, say, hours of work (as in popular “man-hours” term in project), the relative measure no longer works. Hearing i.e. 48 hours, 160 man-hours alters conversation of planning from using story points ever again. People want to continue hearing absolute hours or eventually just impose date.

T-Shirt sizes (S, M, L) or even dog points (Poodle, Labrador Retriever, Saint Bernard) illustrated by Mike Cohn^[1] are means of estimating effort. When followed by deriving duration, they make up schedule. Only by separating them, you’re stepping back from the trap.

Relative size are what people good at^[2]. In contrast, we’re so used to directly go to “when”, blurring effort-then-duration as extra steps behind it.

References

Next read: when to use hours (or days), the [[No Estimate]]

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

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