How to use the Business Days Calculator
- Enter the start date of the period.
- Enter the end date; both endpoints are included in the count.
- Count the public holidays that fall in the range and enter that number.
- Read the working days, already net of the holidays you entered.
- Use the working weeks figure for resourcing and capacity planning.
How the calculation works
The calculation walks the range one day at a time and classifies each date as a weekday or a weekend day using its UTC day number. Iteration rather than a formula is used because it handles partial weeks at both ends of the range automatically, which is where closed-form approximations tend to be off by one.
Public holidays cannot be determined automatically because they vary by country, by state or province, and often by industry agreement. Some also move: Easter follows a lunar calculation, and several jurisdictions substitute the following Monday when a holiday falls on a weekend, which means it should not be double-counted here. Entering the number yourself keeps the result correct for your own calendar.
The Saturday-Sunday weekend is itself a local convention. Much of the Middle East observes Friday-Saturday, Nepal observes a single-day weekend, and shift industries run rosters that ignore the calendar week entirely. For those cases, treat the weekday count as a starting point and adjust for the actual roster pattern.
working days = Σ(days in range where weekday ∉ {Saturday, Sunday}) − holidays enteredSource: ISO 8601 weekday numbering; holiday variation per national labour codes, which must be applied locally.
Worked example
A project runs from 1 September to 31 December 2026, with 3 public holidays in that window.
- Total calendar days in the range: 122.
- Weekend days: 35.
- Weekdays: 87.
- Less 3 holidays: 84 working days.
84 working days, or 16.8 working weeks — the number to use for resourcing, not the 122 calendar days in the contract.
Frequently asked questions
Are both the start and end dates counted?+
Yes, this count is inclusive of both endpoints, which matches how project schedules are usually stated.
Why do I have to enter holidays manually?+
Holiday calendars differ by country, region and sector, and several dates move each year. Manual entry is the only way to stay accurate everywhere.
Can I use a different weekend?+
Not directly. Count the difference in weekend days for your region and adjust the holiday field to compensate.
How many working days are in a year?+
Typically 260 or 261 before holidays, and around 250 after a standard set of public holidays.
Last reviewed August 31, 2026. We review this page whenever the underlying formula, tax year, published rate or standard changes.