How to Calculate Business Days

What is a business day?

A business day (also called a working day) is a day when most businesses, banks, and government offices are open. In most of the world that means Monday through Friday. Saturdays and Sundays are excluded, and so are recognized public holidays.

That single difference — ignoring weekends and holidays — is why “10 business days” almost never equals “10 calendar days.” Ten business days is two full working weeks, which spans 14 calendar days. Add a holiday in the middle and it stretches to 15.

How to count business days by hand

To add a number of business days to a date manually:

1. Start from the day after your start date.
2. If that day is a Saturday, Sunday, or holiday, skip it — it doesn’t count.
3. If it’s a weekday, count it as one business day.
4. Repeat until you’ve counted the number of business days you need.

Example. You’re quoted “5 business days” for a delivery and you order on a Thursday. Friday is day 1, the weekend is skipped, then Monday through Thursday are days 2 through 5. Your delivery lands the following Thursday — a full week later, even though the quote was “5 days.”

Weekends vs. holidays

Skipping weekends is straightforward because they fall on the same days everywhere. Holidays are trickier: they differ by country and even by region, and some shift each year. A few examples of the kind of holidays that affect business-day counts:

• Fixed-date holidays, like New Year’s Day (January 1) or Christmas (December 25), land on the same calendar date every year.
• Floating holidays, like the U.S. Thanksgiving (the fourth Thursday of November) or the U.K.’s spring bank holiday (the last Monday in May), move around the calendar from year to year.
• Easter-based holidays, like Good Friday and Easter Monday, are calculated from the lunar calendar and shift by weeks between years.

Business days in Date Math

Three of the calculators on this site can switch into business-day mode. Tick “Business days only” and the calculation skips every Saturday and Sunday automatically. Tick “Exclude holidays” as well and you can choose a region — the United States, United Kingdom, Canada, or Australia — and the matching public holidays are skipped too.

• Use Add / Subtract to move a specific date forward or backward by a number of business days.
• Use From Now to find a business-day deadline measured from today.
• Use Between Dates to count how many business days fall between two dates.

When you count in weeks or months in business-day mode, the tool treats a business week as 5 working days and a business month as roughly 22 working days, which is the standard convention for working-day estimates.

Where business-day math matters

• Service-level agreements (SLAs). Support and contract response times are almost always written in business days.
• Invoices and payments. “Net 30” terms and bank clearing windows are frequently counted in working days.
• Shipping and fulfillment. Carriers quote transit times in business days, which is why a weekend order feels slow.
• Legal and government deadlines. Filing windows and notice periods are often defined in business days — though the exact rules vary by jurisdiction, so always confirm the official definition.

Key takeaways

• A business day is a weekday that isn’t a public holiday.
• Business days are always equal to or fewer than calendar days over the same span.
• Holidays depend on your country and region, so pick the right one when it matters.
• Date Math counts weekends and holidays for you — just turn on business-day mode and choose a region.