Project Timeline Calculator
Find the finish date for a job that needs a given number of working days, skipping weekends and the days off you list.
Updated Formula covered by automated tests
Give the date work begins and the number of working days the job needs, and the tool returns the date the last day of work is completed, skipping Saturdays, Sundays and any days off you list. It also reports how many calendar days the job spans and how many weekend days fall inside it.
It is meant for the planning question that comes right after an estimate: "the developers say 15 days, so when do we tell the client it ships?" Contractors use it to quote finish dates, agencies to set review milestones, and teachers to map a unit of lessons onto a term. Listing company holidays matters most in late November and December, when a two-week task can stretch to three calendar weeks.
The formula
- W
- Working days of effort needed (a whole number of at least 1)
- working day
- A Monday to Friday that is not in your list of days off
- N(date)
- Serial day number of a date, used to count the calendar span
The start date counts as the first day of work when it is a weekday. That matches how teams talk: a five-day task that starts Monday is done Friday. An earlier version of this tool started counting the day after the start, which pushed every finish date one working day too late (a Monday start for five days ended the following Monday).
Because the rule walks forward one date at a time, it handles any mix of weekends and holidays. A quick sanity check without holidays: every five working days add one full week, so 20 working days from a Monday finish on the Friday three weeks later, 26 calendar days after the start including both ends.
Worked example
A web agency starts a 15-working-day build on Monday, November 16, 2026. The office is closed for Thanksgiving on Thursday, November 26 and the Friday after.
- 1 Week 1, November 16 to 20: 5 working days (5 done).
- 2 Week 2, November 23 to 25: 3 working days (8 done); November 26 and 27 are skipped as holidays.
- 3 Week 3, November 30 to December 4: 5 working days (13 done).
- 4 Week 4, Monday December 7 and Tuesday December 8: 2 more, reaching 15.
- 5 Span: November 16 to December 8 is 23 calendar days = 15 working + 6 weekend days + 2 holidays.
Result: The build finishes on Tuesday, December 8, 2026. Without the two holidays it would have finished on Friday, December 4.
Before you rely on the result
- The schedule assumes one continuous stream of work at a constant pace. It does not model dependencies between tasks, part-time availability or several people working in parallel.
- Days off must be typed in as dates; regional and company holidays are not built in.
Frequently asked questions
Is the end date the day work finishes or the day after?
It is the last working day, the day on which the final unit of work gets done. If you promise delivery "the next business day after completion", move forward one more working day.
What if my project starts on a Saturday?
Weekend start dates roll forward: the first working day becomes the following Monday, and the result shows which date was counted as day 1.
How much buffer should I add to an estimate?
There is no universal figure. Teams often compare past estimates with what actually happened and add the typical overrun, and they list known days off (holidays, planned leave, training) here so the date reflects real availability rather than an ideal week.
Can I plan a schedule where people also work Saturdays?
Not with this tool, which assumes a Monday-to-Friday week. For a six-day week, divide the working days by 6 to get weeks, then convert to calendar days.