Business days in Excel: NETWORKDAYS & WORKDAY

Excel's built-ins are good, provided you feed them the right holidays and the right weekend. Here is how, and where they mislead.

The functions

=WORKDAY(A2, 10, Holidays!A:A)          ' add 10 business days
=NETWORKDAYS(A2, B2, Holidays!A:A)      ' count between dates (inclusive)
=WORKDAY.INTL(A2, 10, 7, Holidays!A:A)  ' 7 = Fri-Sat weekend
=NETWORKDAYS.INTL(A2, B2, 7, Holidays!A:A)

The gotchas

1. The holiday range is on you. Excel ships no holiday data; a stale range silently gives wrong dates. 2. Weekend numbers: the .INTL variants take a weekend code (1 is Sat-Sun, 7 is Fri-Sat); plain WORKDAY always assumes Saturday and Sunday. 3. Substitute holidays (UK Boxing Day observed, etc.) must appear in your range explicitly.

For spreadsheets, paste holiday dates from our free calculator; for applications, the API keeps the calendar maintained for you.