What this calculator does
Count the working days between two dates, or find the date that's a set number of working days away. Shipping estimates, payment terms, notice periods and processing times are often given in business days, not calendar days. Here, a business day means any Monday through Friday. So a five-business-day wait that starts on a Thursday runs into the next week.
This calculator works in two directions. It can count how many business days fall between two dates, and you choose whether the first and last dates count. Or it can start from a date and move forward or backward a set number of business days to find the target date. In both modes, you can allow for public or company holidays that land on weekdays.
Where it's used
Why this math matters outside the classroom:
- Delivery estimates. Ten business days after a Monday falls on the Monday two weeks later when there are no holidays.
- Contract deadlines. Office staff count working days to find a response deadline that skips weekends.
- Payroll. Payroll clerks count the working days in a month to prorate pay for a partial month.
- Project planning. Managers convert a task estimate in working days into a calendar finish date.
How to use it
- Choose whether to count business days between two dates or to add business days to a date.
- Enter the start date. Then enter either the end date or the number of business days to add (use a negative number to go back).
- If holidays fall on weekdays in the period, enter how many. When counting, decide whether the start and end dates should be included.
- Read the business-day count or the resulting date. You'll also see how many calendar days the period covers.
What the inputs mean
- Count the start date if it is a weekday
- When ticked, the start date counts as a business day if it's a weekday. Most "from today" counts include today, but many deadline rules don't.
- Count the end date if it is a weekday
- When ticked, the end date counts too. Tick both to count every weekday from the first date to the last.
- Business days to add
- In add mode, the start date isn't counted. So adding 1 business day to a Friday gives the next Monday.
- Holidays on weekdays in the period
- Only count holidays that fall on a Monday to Friday inside the period. A holiday on a weekend is already left out, so don't enter it.
Formula and method
business days = weekdays in the period − weekday holidays weekdays in the period = calendar days − Saturdays − Sundays add mode: step day by day from the start date, counting only Monday to Friday, until N + H business days are reached
In the add-mode formula, N is the number of business days you want to add, and H is the number of weekday holidays you entered.
For counting, the period depends on your include choices. It starts on the start date or the day after it. It ends on the end date or the day before it. Every run of 7 days in a row holds exactly 5 weekdays. So whole weeks are counted in one go, and the leftover days are checked one by one.
For adding, the start date itself is day zero. The calculator moves forward one calendar day at a time and counts a day only if it's a weekday. It stops when it has counted enough. Each weekday holiday you enter is a day the office is closed, so it adds one more business day to the count.
If the end date you enter is earlier than the start date, the two are swapped, so the count is always positive.
Worked example
Today is Sunday, October 18, 2026, and a project must finish by Tuesday, November 17. Today is counted (it's a Sunday, so it adds nothing), and November 17 is not.
- The period runs from Oct 18 up to, but not including, Nov 17. That's 30 calendar days.
- Those 30 days hold 4 full weeks plus a Sunday and a Monday. So they contain 9 weekend days and 21 weekdays.
- No holidays were entered, so all 21 weekdays are business days.
Result: There are 21 business days available before the November 17 deadline.
Understanding the result
Business-day rules differ. A delivery promised "in 3 business days" usually doesn't count the order day. A notice period set by law may have its own counting rule. Use the include options and the start-date setting that match the rule you're following.
When you add business days, the result is always a weekday. The one exception is adding zero, which gives you the start date itself.
Assumptions and limitations
- Business days are Monday to Friday. Saturdays and Sundays are never business days.
- Each holiday you enter falls on a weekday within the period, and none is counted twice.
- In add mode, holidays are assumed to fall inside the stretch being counted. So each one pushes the result out by one business day.
- The calculator doesn't know any holiday calendar. You decide which holidays apply and enter how many there are.
- In add mode, a holiday that falls after the date you'd get without it may not actually change the answer. Check the date if a holiday sits right at the end of the period.
- Work weeks other than Monday to Friday, such as Sunday to Thursday or six-day weeks, aren't supported.
Frequently asked questions
What is 10 business days from today?
Choose "Add business days", leave the start date on today and enter 10. Today isn't counted, and weekends are skipped. The result is usually 14 calendar days away, or more if holidays fall in between.
Should I count the start date?
It depends on the rule. Counting "from today, including today" means ticking the start option. Most delivery and deadline rules start counting on the next business day. Try both settings to see the difference, which is at most one day.
How do I allow for public holidays?
Count the holidays that fall on weekdays between your dates, and enter that number. They're subtracted from the business-day count. In add mode, they're added to the number of days to move forward.
Why is my answer different from another tool?
Usually it comes down to two things: whether the start and end dates are included, and which holidays are left out. Check those two settings first.
How this calculator is checked
Method: Weekday counting on the Gregorian calendar (5 weekdays per 7 consecutive days); direct day-by-day stepping for add mode. The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-18. Found a problem? Tell us.
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