Business days calculator
The only business-day calculator that shows all three conventions professionals actually argue about — because "how many business days" has three defensible answers.
The three conventions, side by side
| Convention | What it counts | Who uses it |
|---|---|---|
| Inclusive (both ends) | Start and end day each count, if they are workdays | Excel NETWORKDAYS; most spreadsheet users by default |
| Exclusive of start | Counting begins the next business day | Payment terms, SLA clocks, "received on day 0" operations |
| DAYS() + 1 compensation | Plain subtraction, then add 1 back | Workaround formulas in sheets that lack a NETWORKDAYS column |
Same inputs, three answers — that gap is why disputes happen. This page exists so you can see all three before you sign something. Holiday source: OPM federal schedule (verified per year); toggle above switches them off.
Common questions
Which business-day count is "correct"?
All three shown here are in live use. Excel's NETWORKDAYS includes both the start and end date when they are workdays; many business processes instead count from the day after receipt; and a common spreadsheet workaround adds +1 to a plain day subtraction. When a contract matters, the contract's own definition wins — ask when it is silent.
Which holidays are excluded?
U.S. federal holidays as published by the Office of Personnel Management, observed on their observed dates (so July 4 falling on Saturday excludes Friday July 3, 2026). Toggle them off to count pure Monday–Friday days.
What about my company's floating holidays?
Federal holidays are the floor, not your calendar. For company-specific days, turn federal holidays off and subtract your own count manually, or use the inclusive/exclusive pair above as bounds.
Last updated 2026-11-04 · Calculations follow the full leap-year rule (including the year 2100 exception).