Business Days Calculator
Count business days between dates or add business days to a date
How It Works
Overview
A business days calculator counts only weekdays (Monday through Friday) between two dates, or projects a date that is N business days before or after a starting date. It's the standard tool for legal deadlines, shipping ETAs, project planning, contract response windows, and SLA tracking — any situation where weekends shouldn't count toward elapsed time.
This tool subtracts Saturdays and Sundays from the calendar count. It does not automatically subtract public holidays because holiday calendars vary by country, state, and even employer. For an exact figure, take the result and subtract any holidays that fall on a weekday inside your range — typically 10–11 per year in the US, 8 in the UK, 12–15 in many EU countries.
The Formula
Internally the calculator iterates day-by-day from the start date to the end date, using JavaScript's Date object and theisWeekend check to skip Saturdays and Sundays. The "add business days" mode walks forward one calendar day at a time, decrementing a counter only when a weekday is hit, until the requested number of business days has been reached.
A faster closed-form approximation: weeks × 5 + remainder_weekdays. But the day-by-day approach is needed when you want to also detect whether the start or end date itself falls on a weekend.
Worked Example
Counting: From Monday, March 3, 2025 through Friday, March 21, 2025 inclusive:
- Total calendar days: 19
- Weekend days (Saturdays + Sundays): 4 + 2 = 6
- Business days: 19 − 6 = 15
Adding: A contract signed on Thursday, March 6, 2025 allows "10 business days to respond":
- Day 1: Friday March 7
- Day 2–6: Mon–Fri March 10–14
- Day 7–10: Mon–Thu March 17–20
- Deadline: end of day Thursday, March 20, 2025
When to Use This
- Contract and legal deadlines — most US court rules count business days for filings under 11 days.
- Shipping and delivery promises — "3–5 business days" means weekdays in transit, not calendar days.
- Payroll cutoffs — "submit timesheets 2 business days before payday".
- Project scheduling — sprint planning and Gantt charts use working-day duration.
- Vacation and PTO planning — figure out how many actual workdays you'll be away.
- Bank settlement times — ACH transfers and check clearing are quoted in business days.
Common Mistakes to Avoid
- Forgetting holidays. A 5-business-day deadline that crosses Thanksgiving or Christmas is effectively 6+ calendar weekdays. Always cross-check against a holiday calendar.
- Off-by-one inclusion. Some contracts say "within 5 business days of receipt" — does day 1 start on the receipt day or the next day? Read the definitions clause.
- Mixing business and calendar days. A "30-day return policy" is calendar days, not business days. Don't apply business-day math to calendar-day terms.
- Ignoring international weekends. If you're working with partners in Saudi Arabia or Israel, their weekend may differ. Confirm jurisdictions.
- Using business days where SLAs require hours. Many B2B SLAs are in business hours — e.g., 4 business hours during 9–5 weekdays — not business days.
Frequently Asked Questions
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