For core Squad members, the simplest way to start is to find out what availability they have (and are able to foresee) in the sprints of the coming quarter. Do they have annual leave coming up? etc.
Stories should be estimated in story points using the Fibonacci sequence of 1, 2, 3, 5 etc., and Epics maybe be estimated using the t-shirt sizing estimation technique (S, M, L, XL, XXL) but using Fibonacci is the guidance and the minimum sizing for S (small Epic for example) is 21. There is currently a field for this in Jira, which is can use as a placeholder for sizing your Epics until you work out the numbers you are comfortable with.
Here is a recommendation as a guide but sizing effort will vary from squad to squad and from product to product:
Story Points | Effort min. (Days) | Effort max. (Days) |
|---|---|---|
| 1 | 0 | 1.2 |
| 2 | 1.3 | 2.4 |
| 3 | 2.5 | 4 |
| 5 | 4 | 7 |
| 8 | 6 | 11 |
| 13 (too big for sprint - slice it up) | 10 | 17 |
Here is a recommendation as a guide on sizing Epics but this Fibonacci sequence to start may vary from Product to Product
T-Shirt Sizing | Fibonacci # guide |
|---|---|
| Small (S) | 21 |
| Medium (M) | 34 |
| Large (L) | 55 |
| XLarge (XL) | 89 |
| XXLarge (XXL) | 144 |