How to fix t-shirt sizing

T-shirt sizing is the practice where you estimate the effort it will take to complete a task using t-shirt sizes.

It leads people to say things like "That's 2 large, 3 mediums, and 4 smalls" and pretend it's meaningful.

I don't recommend t-shirt sizing. But if for some reason it's useful for you, here's a way to fix it.

Take each of your labels, ie:

• Small
• Medium
• Large

For each one, consider two things: the number of people involved, and the number of days it will take them to get the job done.

Use a range to represent your estimates. If unsure, make the range bigger.

With 90% certainty, we can finish a project labeled "small" with 2 to 3 people over 5 to 20 days.

If many of you are making estimates, take a moment to agree on your definition of each label.

Your estimate might still be imprecise, but now you can add numbers and trust the maths will work. Without a clear definition, you can't divide "Medium" with "Small" and expect a meaningful result.