A project timeline calculator that converts task estimates measured in working days into concrete start and finish dates. Instead of guessing when a project lands, you list each task, say how many working days it takes, chain the dependencies, and the tool schedules everything around your real working week, your weekends and your custom holidays. It is built for freelancers quoting delivery dates, agencies planning sprints, contractors sequencing a build, and anyone who has ever promised a deadline and then realised the bank holidays moved it a week.
How it works
You start by choosing the project start date and marking which days of the week are non-working. Saturday and Sunday are off by default, but you can model a four-day or six-day week with a single click. Then you add tasks, each with an effort in working days. Effort is pure working time: a task estimated at ten working days always consumes ten days of actual work no matter how many weekends or holidays fall inside its span.
Each task can begin at the project start or after another task. When a task depends on a predecessor, the calculator starts it on the next working day after that predecessor finishes, so the whole chain ripples forward automatically. Add a custom holiday and every task spanning that date stretches to absorb it, pushing the finish later without any manual editing. The schedule recomputes the instant you change anything, and a built-in circular dependency check warns you if two tasks ever wait on each other.
The result is a clear table of start and finish dates per task, a four-card summary of the overall project start, finish, total working days and calendar span, and a horizontal Gantt chart that lays the tasks out along a calendar-day axis. When the plan looks right, the Download CSV button exports the full schedule for a spreadsheet or a status report. Everything is saved in your browser, so your plan is still there when you come back.
Example
Say a website redesign starts on a Monday and your team works a standard Monday-to-Friday
week. You enter five tasks: Discovery 5 working days, Wireframes 4, Visual design 6,
Build and QA 10, and Launch 2, each starting after the previous one. With no holidays,
the calculator chains them into a roughly 27 working day plan that spans about five and a
half calendar weeks because of the weekends in between. Add a public holiday in the middle of
the Build and QA phase and the launch date slides one working day later, with the Gantt bar
for that task visibly widening. Switch to a four-day week and the same effort now stretches
across more calendar time, all recalculated live.
Tips
- Keep estimates honest in working days; the tool handles the weekend and holiday maths for you.
- Use the move-up and move-down arrows to reorder tasks without breaking their dependency links.
- Export the CSV at each planning milestone so you have a dated record of how the schedule shifted.