How do you count working days between dates?

Both the start date and the end date count if they are weekdays and not holidays. That matches Excel NETWORKDAYS. Weekends are Saturday and Sunday.

Does add business days count the start date?

No. Adding N business days is Excel WORKDAY: the start date is day 0. Adding 1 to a Friday returns the following Monday (or Tuesday if Monday is a holiday).

Which holidays are used?

Optional US federal observed holidays for 2025, 2026, and 2027 from the OPM schedule (5 U.S.C. 6103), including in-lieu Fridays and Mondays when a holiday falls on a weekend. This is not a guarantee a bank or counterparty is closed. You can add custom dates.

Is Net 15 calendar days or business days?

Trade Net 15 / Net 30 is often calendar days. The invoice Friday helper on this page adds 15 (or 10 / 30) business days, because this is a working-days calculator. Read your contract.

Business Days Calculator — Working Days Between Dates

Q: Is this legal advice?

No. This is calendar math, not legal, payroll, SLA, or collections advice.

Start date

End date

Holidays

Skip US federal observed holidays, 2025–2027

Dates follow the OPM federal holiday schedule (5 U.S.C. 6103), including in-lieu Fridays and Mondays. Federal observed is not a guarantee a counterparty, bank, or court is closed.

Custom holiday (optional)

Result

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How the days are counted

Between dates includes both ends when they are working days — the same rule as Excel NETWORKDAYS. A Monday-to-Friday week is 5 business days. Friday to the next Friday is 6.

Add / subtract treats the start date as day 0, like Excel WORKDAY. Add 1 to a Friday and you land on Monday, unless Monday is a holiday.

Weekend means Saturday and Sunday. There is no half-day, no Saturday-working schedule, and no state holiday pack in this version.

Worked example

Invoice dated Friday, August 21, 2026. Add 15 business days with federal observed holidays on. Labor Day 2026 is Monday, September 7. The due date is Monday, September 14, 2026. With holidays off, it would be Friday, September 11.

Federal observed holidays used here

Copied from the OPM year tabs for 2025–2027. Inauguration Day 2025 is the same date as MLK Day and is DC-area only, so it does not add a second nationwide off-day.

Observed	Holiday	Year

FAQ

How many working days between two dates?

Count weekdays from the start through the end, then subtract any holidays you have turned on. Both dates count if they are working days.

Do you skip US bank holidays?

The toggle skips US federal observed dates from OPM, which is the usual nationwide list. Banks, courts, and private offices can differ. Add a custom chip if your counterparty is closed on another day.

Is the Net 15 helper the same as invoice terms?

Not always. Many contracts mean 15 calendar days. This helper adds 15 business days from the most recent Friday (or from today, for Net 10 / Net 30). Use it when you want working-day slack, not as a reading of your contract.

Is this legal advice?

No. Calendar math only. Not legal, payroll, SLA, or collections advice.

This calculator does calendar math. It is not legal advice, not a filing deadline, and not a guarantee that any office is closed. Confirm holidays with your counterparty. Dates stay in this browser. No account.