CountBusinessDays is a free tool that calculates business days while optionally excluding weekends and U.S. Federal holidays. Here’s how the calculations work.
By default, a business day is any day that is:
You can turn these exclusions on or off for each calculator.
Most calculators let you choose whether the start date and/or end date should be counted. This is useful depending on whether you are measuring the number of days between two events or the duration that includes one or both endpoints.
The tool follows official U.S. Office of Personnel Management (OPM) rules, including the “observed” date when a holiday falls on a weekend:
ISO 8601 week numbering is used:
All date calculations are performed using your device’s local timezone so that the results match the calendar date you see on your computer or phone.
You can add your own company or personal holidays. These are stored only in your browser (using localStorage) and are never sent to any server.