Business Days Calculator

What counts as a business day?

A business day is a date on which the organization doing the work operates. For a Monday–Friday office, that usually means a weekday that is not a holiday or closure. A warehouse working Saturdays or a team working Sunday–Thursday needs a different calendar. Select the days that team does not work, then enter its closures.

This distinction matters when a promise says “three business days.” You need a start date, a workweek, a holiday list, and a rule about counting the start. Without those four inputs, two plausible answers can differ. This calculator makes each assumption visible and keeps a breakdown you can export.

A worked example: three working days after July 2, 2026

Start on Thursday, July 2, exclude the start date, and select the US federal preset. The result is Wednesday, July 8. July 3 is the observed Independence Day holiday in the OPM schedule; the following two dates are the weekend.

With the same workweek and no holidays selected, the result is Tuesday, July 7. That one-day difference comes entirely from the holiday setting.

Load this example in the calculator →

Does the first day count?

For “five working days after Monday,” Monday is day zero. With no holidays, Tuesday is day one and the following Monday is day five. For “working days in a Monday–Friday period,” including both dates gives five. The words describe different counting conventions, so the calculator offers separate start and end switches when counting a range.

An included endpoint still has to be a working day. Checking “Include the start date” does not turn a Sunday or holiday into one. If both inputs are the same date, that date counts once only when both endpoint boxes are checked and it is a working day.

Use the observed holiday, not just its calendar date

Under OPM’s holiday substitution rules, for the standard federal workweek, a US holiday on Saturday is generally observed on Friday; a Sunday holiday is generally observed on Monday. This can cross a year boundary: New Year’s Day 2028 falls on Saturday, so the observed day is December 31, 2027. The preset includes that crossover.

The preset models recurring federal rules, not every US employer, state holiday, stock exchange, or emergency closure. Inauguration Day and one-off closures are not added automatically. Future dates project the current rules. For a different workweek, use custom holidays because the federal rules for days off in lieu can differ.

For the UK, consult the GOV.UK bank holiday lists for the correct nation: England and Wales, Scotland, or Northern Ireland. Enter the listed substitute dates as closures. Do not copy one nation’s list into another team’s plan without checking it.

Why a delivery estimate may still differ

A date calculator cannot determine when processing begins. An order placed after a cutoff on Friday may enter the queue on Monday; shipping might begin only after processing finishes. Start from the date the service actually specifies. If its promise counts that date as day one, include it when counting a range.

The tool counts whole dates. It does not model half-days, hours, or rolling 24-hour periods. A holiday already on a selected day off is excluded once, so the breakdown totals remain consistent. For a contract or official filing, use the calendar and counting rules stated by the organization receiving it.

Check the same calculation in a spreadsheet

For a Monday–Friday range with both endpoints included, Excel’s NETWORKDAYS.INTL accepts a start date, end date, weekend setting, and holiday list. If A2 and B2 contain your dates and H2:H20 contains actual holiday dates, use:

=NETWORKDAYS.INTL(A2,B2,1,H2:H20)

Set both endpoint boxes here to match that convention. To exclude the start date for a range that ends later, use A2+1 as the spreadsheet’s start. The holiday list must include the same observed and custom closures you selected here.

How this calculator handles dates

Dates are counted as Gregorian calendar dates, so a daylight saving change cannot add or remove a working day. Range calculations support up to 3,660 days; adding or subtracting supports up to 500 working days. Adding zero returns the original date, even if it is a day off. The on-screen audit shows the first 100 dates; the CSV includes the full calculation.

For every date, the tool checks your endpoint rule first, then your days off, then holidays. A date receives one category. Custom holiday entries are checked for valid dates and duplicates are removed. See our calculation methodology or report a correction with the inputs that produced it.

Sources checked September 30, 2026: OPM federal holiday schedules, OPM holiday substitution rules, GOV.UK bank holidays, and Microsoft’s NETWORKDAYS.INTL documentation.