Calculator
Count working days between two dates, check how many business days it's been since (or until — or till, if you want) a date, or add business days to today — weekends excluded automatically, holidays optional. Whether you think of it as a business days calculator or a business day calculator, this covers both directions.
All four modes count only Monday through Friday as business days. If you leave the holiday checkbox on, they also skip a small default set of fixed-date holidays (New Year's Day, July 4th, and Christmas) — a reasonable approximation, though it won't know about moveable holidays like Thanksgiving or region-specific public holidays, since those vary by country and even by state or province. "2 to 5 business days from today," for example, gives you the earliest and latest date a shipment or reply is likely to arrive, skipping any weekend in between.
For a simpler count that includes every calendar day, use the Date Difference Calculator instead.
Reference
Related
Count every calendar day instead of just working days.
Shift a date forward or backward by a day count.
Check whether a specific date is a weekend.