T-shirt sizing - Estimating workload and capacity without false precision

T-shirt sizing is a great way of estimating the relative size or level of effort of a set of tasks. Effort and cost discussions are significantly easier when decoupled from hours and dollars. It lets people focus on the problem definition and possible approaches without getting hung up on absolute values.

  1. Size some work items relative to each other. "This one feels maybe twice the size of this other one". 
  2. Bin the sorted items in arbitrary groups (T-Shirt sizes) Small, Medium, Large, etc. based on the amount of work or complexity.  
  3. New items are sized the same way when they are first introduced. They are compared to the existing backlog and slotted into the buckets.
This process gives you a feel for work and relative complexity without resorting to false precision for specific days and hours. Velocity and Capacity can be extrapolated later after tasks of various sizes are completed. Start with relative sizing and then iterate closer to absolute sizing as you know more.

People struggle with sizing.  Management wants to how much it will cost or how many people and days it will take.  We want to provide a way of describing effort before we really know what a unit of work costs or hours they take. The two most common issues are
  1. The desire for precise estimates before enough is known for those estimates to be real.
  2.  Confusion on whether the size represents complexity or the amount of work. It represents both.  This is not precise.  It can't be.  Assume that complexity and scope combine in some way to create a single value that will eventually convert into hours and material. 

Plan, Do, Measure, Adjust

You'll have to work out the size ranges for Small Medium and Large and then possibly adjust them.  I tend to use Planning Poker style Fibbonici sizing for bin sizes.  In other situations,  just the notion of size being a couple times larger than the previous bucket is good enough.


You can find Agile sizing techniques via any search engine.  Wikipedia has a general article on software sizing.

Revision History

Created 2024 02


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