glossary — plain english
Duration
How long a task takes in calendar time, start to finish — which is not the same as how much work it contains.
Duration is the width of a task's bar: the time between its start and finish. Effort is the hours of work involved. Two days of work spread across two weeks because of approval waits has a two-week duration.
Use the precision you can support. "About two weeks" is a useful starting estimate. Scheduling software can combine durations with dependencies to calculate dates and update later tasks when an estimate changes.
If a task is too large to estimate, split it into smaller pieces. Then estimate a range to show how much uncertainty remains.
See it on a real chart
Describe your project in plain English and ganttchart.ai turns it into a Gantt chart you can edit and share. Or read the method first: the plain-English planning guide.