DueDateThe one-day difference
Excel's NETWORKDAYS(start, end, holidays) counts both the start date and the end date if they are workdays. This calculator counts the days after the start date up to and including the end date, which is how deadline and "within N business days" counts usually work. So when the start date is a business day, NETWORKDAYS returns one more.
Worked example (United States holidays)
December 1 to December 31, 2026, with Christmas Day as a holiday:
- This calculator: 21 business days (prefilled above).
- NETWORKDAYS: 22, because Tuesday, December 1 is also counted.
To reproduce a NETWORKDAYS result here, set the start date one day earlier: November 30 to December 31, 2026 gives 22.
WORKDAY matches the add mode
Excel's WORKDAY(start, days, holidays) does not count the start date, which is the same as the add business days mode here. The difference is that this calculator fills in public holidays for you, so you do not have to maintain a holiday list in your spreadsheet.
The same calculation is available as a JSON API, so you can run it inside an accounting, ERP or workflow system. Get a free API key (1,000 requests a month) or read the OpenAPI spec.
Holiday data comes from an open-source dataset and may be incomplete, especially for regional, ad-hoc or newly declared holidays. Check legally or financially critical deadlines against an official source.
Frequently asked questions
Why does NETWORKDAYS give one more day?
NETWORKDAYS includes the start date when it is a workday; this calculator excludes the start date.
Do I need a holiday range?
Not here. Pick a country and optional region and public holidays are applied automatically. In Excel you must supply them yourself.
Does it support custom weekends like NETWORKDAYS.INTL?
No. Weekends are always Saturday and Sunday.