Date Duration Calculator
Enter a start date and an end date to find the exact number of days, weeks, and business days (weekdays only) between them — useful for deadlines, contracts, and project planning.
How the Date Duration formula works
Total duration is a straightforward date subtraction:
Total days = (End date − Start date) in days Weeks = Total days / 7 Business days = Total days − (2 × number of full weekends in the range)
Step-by-step calculation
- Subtract the start date from the end date to get the total number of days.
- Divide by 7 to express the duration in weeks.
- Walk through each day in the range and count how many fall on a Saturday or Sunday.
- Subtract the weekend day count from the total to get business days.
Worked example
From March 1 to March 31 (30 days total): that's 4 full weekends plus a couple of extra weekend days, for roughly 8–9 weekend days, leaving about 21–22 business days — the exact count depends on which day of the week March 1 falls on.
Frequently asked questions
Does the calculator count the start date, the end date, or both?
It counts the number of full days between the two dates (end minus start), so the start date itself isn't counted as a full elapsed day — this matches how most deadline and contract-length calculations work.
Does 'business days' account for public holidays?
No — it excludes Saturdays and Sundays only. Public holidays vary by country and region, so you'd need to subtract those manually for your specific calendar.
Can I calculate a date duration into the future?
Yes — enter any two dates in either order; the calculator will show the absolute duration between them regardless of which one is earlier.