How to Calculate Business Days in Excel

Whether you're tracking project deadlines, calculating invoice due dates, or figuring out how long a process actually takes — counting calendar days rarely tells the full story. Business days are what matter, and Excel has dedicated functions built specifically for this kind of work.

Here's exactly how those functions work, what variables affect the results, and why the "right" approach depends entirely on your situation.

What Counts as a Business Day?

A business day is any weekday that isn't a public holiday — typically Monday through Friday, excluding recognized holidays. The challenge is that weekends are universal, but holidays vary by country, region, company, and industry.

Excel's built-in date functions handle the weekend exclusion automatically. Holiday exclusion, however, requires you to supply that data yourself.