Business days calculator

How the days are counted

This is not a worldwide holiday database. It is three counting rules on one page, so you can match the one your invoice or SLA actually uses.

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.

Invoice / Net 30 uses calendar days, which is how most trade terms are written. Invoice dated Friday, August 28, 2026 plus 30 calendar days is Sunday, September 27, 2026. Turn on “due on business days only” and that Sunday moves to Monday, September 28. Labor Day 2026 is Monday, September 7 — it sits inside the 30 days but does not change a Sunday due date.

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

Worked example (business days, not trade Net 15)

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. Trade Net 15 is still calendar days — use Invoice / Net 30 for that.

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.

FAQ

How many working days are between two dates?

Both the start date and the end date count if they are weekdays and not in the holiday set. That is the same rule as Excel NETWORKDAYS. Saturday and Sunday are weekends. A Monday-to-Friday week is 5 business days; Friday to the next Friday is 6.

When is a Net 30 invoice due?

Net 30 is 30 calendar days after the invoice date. The invoice date is day 0, so you add 30. An invoice dated Friday, August 28, 2026 is due Sunday, September 27, 2026 on the calendar. If payment is only accepted on a business day, turn on “due on business days only” and it moves to Monday, September 28. Labor Day 2026 is Monday, September 7 — it sits inside the 30 days but does not move that Sunday due date.

Is Net 30 calendar days or business days?

Most trade terms — Net 15, Net 30, Net 45, Net 60 — mean calendar days. Use Invoice / Net 30 for that. Add / subtract is different: it uses Excel WORKDAY (business days only), which is useful for SLAs, not for reading an invoice. Read your contract.

What if a Net 30 due date falls on a weekend or holiday?

Invoice mode still prints the calendar due date. Check “due on business days only” to roll a Saturday, Sunday, or US federal observed holiday forward to the next weekday that is not in the holiday set. The term itself does not skip weekends while counting — only the landing day can move.

Which holidays does this skip?

Optional US federal observed dates for 2025, 2026, and 2027, copied from the OPM federal holiday schedule (5 U.S.C. 6103), including in-lieu Fridays and Mondays when a holiday falls on a weekend. That is not a guarantee a bank, court, or counterparty is closed. Add a custom date if your buyer observes something else. In invoice mode these dates only move the due date when “due on business days only” is on.

How do I add N business days to a date?

Switch to Add / subtract. The start date is day 0, like Excel WORKDAY. Add 1 to a Friday and you land on Monday, unless Monday is a holiday. Negative numbers go backward. The “Net 30 business days” preset is this mode — it is not trade Net 30.

Is this legal advice?

No. This is calendar math, not legal, payroll, SLA, or collections advice. Holidays are US federal observed dates from OPM, not a filing deadline and not a promise that any office is closed. Confirm terms with your counterparty.