How a formula automatically calculates how many days a task took, based on the start and end date

A formula in the task template automatically calculates how many days a task took: once you fill in the start date and, later, the end date, the system subtracts the two values and shows the result in positive or negative days.

Why automate this calculation?

Manually measuring how long each task took is tedious and error-prone, especially on teams juggling many tasks at once. An automatic formula removes that work and also reveals whether the task was finished within the expected deadline or not.

A negative-day result indicates a delay; a positive-day result means the task was finished ahead of schedule — a simple way to measure team performance.

How it works in practice

When creating the task, fill in the project's start date.
Set the expected deadline (7 days by default, but adjustable to 2, 5, 15 days, whatever makes sense).
When the task is marked as complete, the formula automatically calculates how many days it took.
The result appears directly on the card, with no manual calculation needed.

Formula result	What it means
Positive days	Task completed ahead of schedule
Negative days	Task completed late

Why choose Jestor

Fully editable formulas, no technical knowledge needed to adjust the default deadline.
Automatic indicators that roll this data up into team-tracking charts.
Ready-made task template that still adapts to any deadline your company uses internally.

FAQ

Do I need to fill in the end date manually?

Yes, the calculation depends on both the task's start date and end date being filled in.

Can I change the default 7-day deadline?

Yes, the deadline is configurable in the formula and can be adjusted to any number of days.

Does this calculation also work for subtasks?

Yes, both tasks and subtasks use this same kind of automatic calculation. See more at jestor.com.

Reference video

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