This extension will allow you to calculate your capacity for a given iteration
This shows the capacity in hours instead of story points and doesn't take into account the 3 sprint average point velocity of a team. Not sure what the formula is based on, but it seems faulty.
JIRALyzer
vanillabagel
phsgpacalc
https://jiraassistant.com
Caesar Goz
https://noahcoffey.com
Matt Carlucci
ZedXagE
Key Building Blocks
Jui-Shan (Jenny) Liang
kelvin hung
https://codek.org