The responsibility of estimating how long a task will take belongs to the:

A project scheduler organizes and maintains the schedule tool and timeline but relies on the team's input for duration estimates rather than generating them independently.

The project team is responsible for estimating task durations because team members have direct technical knowledge of the work involved. This bottom-up estimating approach leverages subject matter expertise, producing more reliable estimates than those generated by managers who may not perform the work themselves.

The project manager facilitates and oversees the estimating process but delegates the actual estimation to team members who understand the technical effort required.

A project coordinator handles administrative and logistical tasks and does not have the technical authority or expertise to estimate task durations.