Business Days Calculator
Count calendar days or working days between two dates, with optional end-date inclusion and custom holiday exclusions.
Dates and workweek rules
First date in the interval.
Must be on or after the start date.
Choose a five-day, six-day, or all-days calendar.
Optional custom dates; duplicate dates are counted once. Up to 50 dates.
Live results
Boundary dates included by the current setting.
After the selected weekly rest-day rule, before custom holidays.
Days removed by the selected workweek rule.
Unique listed holidays that would otherwise be workdays.
20 business days from May 1, 2026 through May 31, 2026.
Day-count breakdown
| Metric | Count | How it is determined |
|---|---|---|
| Calendar days in interval | 31 | May 1 through May 31, including the end date. |
| Eligible workweek days | 21 | Monday through Friday under the selected rule. |
| Weekend days excluded | 10 | Saturdays and Sundays removed from the interval. |
| Custom holidays excluded | 1 | May 25, 2026 is listed and otherwise eligible. |
| Business days | 20 | Eligible workweek days minus qualifying custom holidays. |
How to use this Business Days Calculator
What this calculator does. This calculator counts the days in a date interval and then applies a workweek rule and any custom holiday exclusions to produce a business-day total. It is useful for planning operational lead times, service windows, internal deadlines, shipping estimates, project milestones, or any schedule where “days” and “business days” are not interchangeable. The result is a calendar calculation, not a legal determination of a deadline: contracts, courts, regulators, employers, carriers, and countries can define business days differently. In U.S. federal contexts, a commonly used definition is Monday through Friday excluding legal public holidays; for an example of a formal definition, see the business-day definition in 31 CFR § 802.201.
When to use it. Use it when you need to count working days across a project window, estimate how many office days remain before a due date, compare a five-day workweek with a six-day workweek, or remove organization-specific closures from an otherwise regular work calendar. It is also handy for checking a vendor promise stated as “within 10 business days” or for documenting the exact assumptions behind a schedule shared with colleagues.
How to calculate
- The calculator opens with a complete demonstration: May 1, 2026 to May 31, 2026, the end date included, Saturday and Sunday excluded, and May 25, 2026 entered as a custom holiday. The example workbook is validated in the browser on first load, so Download Excel is immediately available.
- Replace Start date and End date with your own ISO-style date values using the native date controls. The end date must not precede the start date.
- Choose Business days: exclude Saturday and Sunday for a standard five-day workweek, exclude Sunday only for a six-day Monday-through-Saturday pattern, or count every calendar day.
- Set Include end date according to your counting convention. When it is off, the interval stops immediately before the end date; when it is on, the end date can contribute one additional day if it satisfies the workweek and holiday rules.
- Add any Holidays to be excluded. Each holiday is optional, must be a valid date, and is counted at most once even if entered twice. A holiday outside the interval or on an already excluded weekly rest day does not reduce the answer.
- Read the live result cards and the day-count breakdown, then use Download Excel to export the current canonical values and assumptions as a real .xlsx workbook. Reset clears the demonstration dates and holiday rows; after Reset, Excel export stays disabled until a complete valid date range is entered again.
Input guide
Start date is required and accepts a calendar date between 1900-01-01 and 2200-12-31; for example, 2026-05-01. Moving it later generally shortens the interval. A common mistake is assuming the start date is automatically excluded: in this calculator it is always the first potential counted date. End date is also required, uses the same date range, and must be on or after Start date; 2026-05-31 is the demonstration value. Moving it later usually increases the count, while a date before Start date is rejected. The calculator limits one interval to 100 years so an accidental extreme entry cannot trigger an impractically large day-by-day evaluation.
Business days is a required rule selection. “Exclude Saturday and Sunday” models a Monday-through-Friday week; “Exclude Sunday only” models Monday through Saturday; “Count every calendar day” applies no weekly exclusion. Changing this control can materially change the total, so match it to the organization or jurisdiction you are planning for. Include end date is a required Boolean choice: checked means the end date participates in the interval, unchecked means it is a boundary after the last counted date. The difference is often one calendar day, but it may be zero business days if the end date is a weekend or custom holiday.
Holidays to be excluded is an optional collection of up to 50 valid dates; the demonstration uses 2026-05-25. Use it for public holidays, plant shutdowns, company closures, or any non-working date that is not already removed by the weekly rule. Duplicate dates are harmless because they are deduplicated. Do not assume a U.S. federal holiday list automatically applies to your employer: the U.S. Office of Personnel Management federal holiday schedule is authoritative for federal employee holiday observances, while private organizations can follow different schedules.
Output guide
Business days is the primary exact count under the assumptions you entered. Calendar days in interval counts all calendar dates in the selected interval before any weekly or holiday exclusions. Eligible workweek days is the number remaining after the selected weekly rest-day rule but before custom holidays. Weekend days excluded is the number removed specifically by that weekly rule; it can be zero when every day is counted. Custom holidays excluded counts unique listed dates that fall inside the interval and would otherwise have been eligible workdays. The four summary pills repeat these same canonical values in compact form, and the Day-count breakdown table presents the same totals with an explanation of each step.
Worked example
From May 1 through May 31, 2026 with the end date included, there are 31 calendar days. Under a Monday-through-Friday workweek, 10 weekend days are removed, leaving 21 eligible workweek days. Memorial Day on May 25 is entered as a custom holiday and falls on a Monday, so it removes one otherwise eligible day. The final result is therefore 21 – 1 = 20 business days. The initial result card, summary pills, breakdown table, and downloaded workbook all use these same typed values.
Learn more. Federal holiday rules are not universal workplace rules. The legal public holidays listed in 5 U.S.C. § 6103 establish the federal statutory schedule, while the U.S. Department of Labor holiday-pay guidance explains that federal labor law does not generally require private employers to pay for time not worked on holidays. For deadline-sensitive work, verify the governing contract, policy, statute, or agency rule rather than relying on a generic calendar convention.
How the counting model works
The calculator uses civil calendar dates in a timezone-neutral way, so daylight-saving changes do not add or subtract a day. It walks from the start date to the last included date, classifies each date against the selected weekly rule, and then excludes any unique custom holiday that would otherwise qualify. This sequence prevents double-counting a holiday that already falls on an excluded weekend. The same canonical model supplies the visible cards, the breakdown table, the accessible live summary, and the Excel workbook.
Practical interpretation and common mistakes
- Confirm the boundary convention. “Between” two dates can mean end-exclusive or inclusive depending on the context. Use Include end date deliberately and document the choice.
- Confirm the local workweek. Monday through Friday is common, but some organizations operate six days or use different weekly rest days. This calculator specifically supports the three reference-style options shown above.
- Enter observed closures, not assumptions. A holiday's observed date may differ from its calendar date. OPM notes, for example, that when certain U.S. federal holidays fall on Saturday or Sunday, an adjacent weekday may be treated as the holiday for many federal employees.
- Do not double-subtract. A custom holiday on an already excluded Saturday or Sunday is recorded but does not reduce the business-day total again.