How to Calculate Business Days: Turnaround Times, SLA Deadlines & Holiday Rules
Understanding calendar days vs. business days in commercial contracts, banking settlement periods, and spreadsheet formulas.
- What constitutes a business day under US law and banking?
- How do you calculate 30 business days from a given date?
- Which US federal holidays are excluded from business day calculations?
- How do you write a business day formula in Excel or Google Sheets?
1. The Definition of a Business Day
Under standard United States commercial and banking conventions, a business day is defined as any official working day from Monday through Friday, excluding statutory federal bank holidays.
Calendar days include every consecutive 24-hour day without interruption. Confusing the two terms in commercial agreements can cause contract disputes and missed delivery deadlines.
2. The Mathematical Day Counting Method
To determine the number of business days between any two dates, count the total calendar days, subtract all weekend days (Saturday and Sunday), and subtract any scheduled federal holidays that occur on weekdays.
For example, a 30-calendar-day month typically contains 20 to 22 working business days.
3. US Federal Holiday Observation Rules
Federal law (Title 5 United States Code Section 6103) establishes 11 permanent statutory federal holidays.
When a fixed-date federal holiday falls on a Saturday, the preceding Friday is observed as the official non-working holiday. When a holiday falls on a Sunday, the following Monday is observed.
| Federal Holiday | Date / Schedule Rule | Banking & Government Status |
|---|---|---|
| New Year Day | January 1 | Closed (Observed Fri if Sat, Mon if Sun) |
| Martin Luther King Jr. Day | Third Monday in January | Closed |
| Washington Birthday (Presidents Day) | Third Monday in February | Closed |
| Memorial Day | Last Monday in May | Closed |
| Juneteenth National Independence Day | June 19 | Closed |
| Independence Day | July 4 | Closed |
| Labor Day | First Monday in September | Closed |
| Columbus Day / Indigenous Peoples Day | Second Monday in October | Federal Offices Closed |
| Veterans Day | November 11 | Closed |
| Thanksgiving Day | Fourth Thursday in November | Closed |
| Christmas Day | December 25 | Closed |
4. Turnaround Times and Contract SLAs
If a vendor contract stipulates a "10 business day turnaround time" starting on a Monday, the deadline falls on the second Friday thereafter, assuming no federal holidays intervene.
If a holiday like Memorial Day occurs during that period, the delivery deadline automatically shifts to the following Monday.
5. Spreadsheet Formulas (NETWORKDAYS and WORKDAY)
In Microsoft Excel or Google Sheets, calculate business days between dates using NETWORKDAYS, or calculate a target end date using WORKDAY:
=NETWORKDAYS(A2, B2, $H$2:$H$12)Cell A2 is start date, B2 is end date, and H2:H12 is a list of holiday dates to exclude.
Frequently Asked Questions
Direct answers to the most common questions people ask online about this topic.
What happens if a legal deadline falls on a weekend or federal holiday?
Under Federal Rule of Civil Procedure 6(a), if the last day of a statutory deadline falls on a Saturday, Sunday, or legal holiday, the period continues to run until the end of the next day that is not a weekend or holiday.
Are bank business days different from corporate business days?
Banks strictly observe all 11 federal holidays and close Federal Reserve ACH settlement windows. Some private corporations remain open on minor federal holidays like Columbus Day or Veterans Day.
How do you calculate 30 business days from today?
Count forward 6 full weeks (5 business days per week = 30 days) and add extra days for any observed federal holidays that fall within that 6-week window.