How to Calculate Business Days Between Two Dates
“3 business days” and “3 calendar days” are very different deadlines, and mixing them up is a common, costly mistake for contracts, shipping, and invoices. Here’s exactly how to count business days by hand, and when to use each type of count.
Calendar days vs. business days
A calendar day is any day. A business day is Monday through Friday, excluding weekends and, depending on the context, public holidays. A 30-calendar-day period typically contains only 20-22 business days, since roughly 2 of every 7 days fall on a weekend.
How to count business days manually
- Count the total calendar days between your two dates, including both endpoints if your context requires it.
- Identify how many full weekends fall within that range; each full week contributes 2 weekend days.
- Subtract the weekend days from the total.
- Subtract any public holidays that fall on a weekday within the range.
Worked example
Counting business days from Monday, March 2 to Friday, March 20:
| Step | Count |
|---|---|
| Total calendar days (inclusive) | 19 |
| Weekend days in range | 4 |
| Holidays on weekdays in range | 0 |
| Business days | 15 |
Get the raw calendar-day count instantly with our date calculator, then subtract weekends manually using the method above for a business-day figure. See our fuller list of common date calculation mistakes for more traps like this.
Where business days actually matter
- Bank transfers, which commonly cite “3-5 business days” rather than calendar days.
- Net 30/60/90 invoice terms, though these are often calendar days unless the contract specifically says “business days”, always check the wording.
- Legal and contract deadlines, where courts and government agencies frequently use business-day counting.
- Shipping estimates, which almost always exclude weekends.
Common mistakes
- Assuming “days” always means business days, or vice versa, without checking the specific contract or policy wording.
- Forgetting to check for holidays that fall within the range, which can silently shift a deadline.
- Miscounting whether the start date is included, since some contexts start counting the day after the trigger event, not the day itself.
- Not accounting for regional holiday differences when working across countries, a business day in the US may be a public holiday elsewhere.
How many business days are in 30 calendar days?
Typically 20-22 business days, depending on where the weekends fall within that 30-day span and whether any holidays occur during it.
Does “3 business days” include the day I’m counting from?
Usually not, most business-day counts start from the day after the triggering event (like a bank transfer initiation or contract signing), but always confirm with the specific policy, since conventions vary.
What’s the difference between Net 30 and 30 business days?
Net 30 typically refers to 30 calendar days unless the contract explicitly specifies business days, which would extend the actual deadline further out due to weekends.
Written by EquateWorld Team
Part of the EquateWorld editorial team.
