Project End Date Calculator

Project the end date from a start date, duration and non-working days.

About Project End Date Calculator

Working-day durations must be walked forward because the weekends crossed depend on the start weekday. Ninety working days spans about eighteen calendar weeks rather than thirteen. Quoting a project end date from calendar arithmetic rather than working days is how deadlines end up roughly 40 per cent too optimistic.

Formula

Project End Date

Step forward from the start date, counting only working days until the duration is met

holiday allowance: Holidays extend the calendar span without advancing the working-day count

Worked example

With the default values below, Project End Date Calculator returns Projected End Date of 2025-08-13. Change any input above and every figure here is recalculated in your browser.

Inputs used

Start date yearaccepts 1,970–2,200: 2,025
Start date monthaccepts 1–12: 4
Start date dayaccepts 1–31: 1
Duration in working daysaccepts 0–2,000 days: 90 days
Public holidays in the periodaccepts 0–100 days: 6 days

Results

Projected End Date: 2025-08-13
Calendar Days Required: 134 days
Calendar Weeks: 19.14 weeks
End Day of the Week: Wednesday
Weekend Days in the Period: 38 days

Step by step

1Values used
2Project End Date
3Projected End Date= 2025-08-13
4Calendar Days Required= 134 days
5Calendar Weeks= 19.14 weeks
6End Day of the Week= Wednesday
7Weekend Days in the Period= 38 days

Assumptions and limits

The result is derived only from the 5 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax or fees or charges into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is Project End Date calculated?

Step forward from the start date, counting only working days until the duration is met Working-day durations must be walked forward because the weekends crossed depend on the start weekday. Ninety working days spans about eighteen calendar weeks rather than thirteen.

Why does Project End Date matter?

Quoting a project end date from calendar arithmetic rather than working days is how deadlines end up roughly 40 per cent too optimistic.

What values do I need to enter?

This calculator takes 5 inputs: Start date year, Start date month, Start date day, Duration in working days, Public holidays in the period. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.