How to Count Business Days Between Two Dates

If you’ve ever tried to figure out when a “5 business day” shipping window actually ends, or how much runway you really have before a deadline, you’ve probably counted on your fingers and second-guessed yourself. The math itself is simple once you know the rule; the tricky part is usually whether the start and end dates both count, and what happens when a weekend lands in the middle.

What counts as a business day

A business day, in the simplest and most common definition, is any day that falls Monday through Friday. Saturdays and Sundays are excluded. That’s it, no other logic is layered on by default.

Two things trip people up:

• Inclusive counting. Both the start date and the end date are included in the total, as long as each one falls on a weekday. If your start date is a Saturday, it doesn’t count toward the business day total, but it’s still part of the calendar span.
• Weekends only, not holidays. This kind of count only removes Saturdays and Sundays. It has no idea that July 4th or Thanksgiving exists. That distinction matters enough that it gets its own section below.

The formula

The underlying logic is a walk through every calendar day in the range, checking each one:

For each day from Start Date to End Date (inclusive):
  If the day is Saturday or Sunday: count it as a weekend day
  Otherwise: count it as a business day

Business Days = count of weekday days in the range
Weekend Days = count of Saturday/Sunday days in the range
Total Calendar Days = Business Days + Weekend Days

There’s no shortcut formula involving division by 7 that works cleanly in every case, because the position of the start day within the week changes how many weekends get caught in a given span. Walking day by day (or using a calculator that does it for you) is the reliable approach, and it avoids the small off-by-one mistakes that creep in when someone tries to do this math from memory on a busy afternoon.

Worked example 1: a single business week

Say your start date is Monday, August 10, 2026, and your end date is Friday, August 14, 2026.

• Walk through each day: Mon, Tue, Wed, Thu, Fri, all weekdays.
• Business days: 5
• Weekend days: 0
• Total calendar days: 5

Because the range starts on a Monday and ends on a Friday, every single day in it is a business day. There’s no weekend to subtract, so the business day count and the calendar day count are identical.

Worked example 2: a range that spans two weekends

Now stretch the same start date out further: start date Monday, August 10, 2026, end date Sunday, August 23, 2026.

• Total calendar days in the span: 14
• That 14-day window contains two full weekends (Aug 15 to 16, and Aug 22 to 23), which is 4 weekend days.
• Business days: 14 total days minus 4 weekend days = 10

So a two-week span here gives you 10 business days, not 14, and not some rounded estimate. This is the exact kind of case where hand-counting on a calendar gets error-prone: it’s easy to miscount how many weekends actually fall inside the range, especially when the start day isn’t a Monday.

The catch: holidays aren’t excluded

This is the single most important caveat to understand about a basic business day count. It excludes weekends only. It does not know about New Year’s Day, Independence Day, Thanksgiving, Christmas, or any other public or company holiday.

That means if you’re counting business days across a range that includes, say, the Fourth of July, a basic calculation like the one above will show one more business day than a company calendar that also blocks out the holiday. If you need a holiday-aware count, the practical fix is simple: run the weekday count first, then subtract one for each recognized holiday that falls inside your date range on a weekday. There’s no way to automate that step generically, because holiday calendars differ by country, state, and even by company.

FAQ

Does a business day count include the start and end dates? Yes, as long as each one falls on a weekday. Both endpoints of the range are included in the total, not just the days strictly between them. If you need to exclude one end, shift that date by a day before you count.

Why does a two-week range sometimes show 9 business days and sometimes 10? It depends on which day of the week the range starts on. A 14-day span that starts on a Monday captures exactly two full 5-day workweeks, giving 10 business days. Shift the same 14-day span to start on a different weekday and it will still contain 4 weekend days, but exactly which calendar dates those are changes, which can shift the total by a day depending on where the range’s edges fall.

Should I use a business day count for legal or contractual deadlines? Be careful. Many contracts, court rules, and government notices define “business days” to exclude specific holidays in addition to weekends, and some define it differently depending on jurisdiction. Treat a basic weekday count as a starting point, then check the specific document or rule that governs your deadline for its own definition before you rely on the number.

Use the Business Days Calculator to run your own numbers.