The T-Shirt Size is a relative estimation technique used in agile projects. Rather than using a number of planning pokers, here, Items are classified into t-shirt sizes: XS, S, M, L, XL, XXL…
T-Shirt Sizing is great when you need to arrive at only a rough estimate of size. Use it to filter out stories that are too big and should be broken down further. Or use it when you are picking from among projects that are already large.
Create and configure the custom field
To create and configure the T-Shirt size custom field, you must be logged in as a user with Jira Administrator permissions.
Go to Settings → Issues → Custom Fields
Create a new custom field of type CFS - T-Shirt Size
Add name and description
Associate the field to the appropriate screens. You must associate a field to a screen before it will be displayed.
Click on 1 Context and click Create, edit or delete contexts on the dialogue.
Click Edit custom field config.
Set description for T-Shirt values.
Steps 5, 6 and 7 are not required. You can use the default values that are set in the app configuration screen.