The best way we have seen to estimate in agile is by planning poker. Planning poker combines expert opinion, analogy, and wideband Delphi into an enjoyable approach to estimating user stories or epics into a reliable estimate. Participants in planning poker include all of the developers on the team that includes developers, testers, user experience [...]
There are many commercial tools available. But, here in this post we have list free tools that are used for Agile/Scrum project management.