What counts as a business day
A business day here is Monday to Friday, excluding the eleven US federal holidays. When a federal holiday falls on a Saturday it is observed on the preceding Friday; when it falls on a Sunday it is observed on the following Monday. We skip the observed day, because that is the day offices are actually shut.
The eleven are New Year's Day, Martin Luther King Jr. Day, Presidents' Day, Memorial Day, Juneteenth, Independence Day, Labor Day, Columbus Day, Veterans Day, Thanksgiving and Christmas Day. Our table runs through 2030 and is documented at where our holiday dates come from.
Three conventions that actually differ
Most disagreements between business-day calculators come down to three choices, and a calculator that does not state them is not usable for anything that matters.
- Does the start day count? We do not count it. Ten business days from a Monday is the Monday two weeks later.
- Observed or actual holiday? We skip the observed day. Independence Day 2026 falls on a Saturday, so Friday 3 July 2026 is the non-working day.
- Whose holidays? Federal only. State holidays, bank holidays and court holidays all differ — Patriots' Day closes Massachusetts courts and nothing else. If your deadline is set by a court rule, check that court's calendar.
Worked example — a 15-business-day response window
A response due within 15 business days of Monday 14 December 2026 is due Wednesday 6 January 2027. The count skips six weekend days plus Christmas Day on Friday 25 December and New Year's Day on Friday 1 January. In plain calendar days that is 23 days — eight days longer than 15, which is the gap that catches people out over the holidays.
Worked example — net-30 in working days
Thirty business days from Monday 14 September 2026 is Tuesday 27 October 2026. The count steps over twelve weekend days and Columbus Day on Monday 12 October, so it spans forty-three calendar days to deliver thirty working ones. Thirty calendar days from the same start is 14 October, a Wednesday. Thirteen days apart on wording that looks identical, which is why invoice terms have to say which they mean.
Why this cannot be answered by a search snippet
Business-day arithmetic depends on a holiday table and a weekend rule, and both vary by jurisdiction and employer. That is also why the answer is worth showing its working: this page names every holiday it skipped, so you can check it against your own calendar rather than trusting a number.
The rule of thumb, and when it breaks
Across a long span, business days run at about 5/7 of calendar days — roughly 71%. Inverted, a target in business days takes about 1.4 times as many calendar days. That estimate is good to within a day or two for spans of a month or more away from the holiday season, and it is badly wrong for short spans and for anything crossing late December. 2026 contains 250 business days out of 365; 2027 contains 249 out of 365; 2028, a leap year, contains 250 out of 366. The variation comes from how many federal holidays land: one falling on a Saturday is observed on the preceding Friday, so New Year's Day 2028 removes a working day from December 2027 and leaves 2027 with twelve observed closures rather than eleven.
Worked example — ten business days, and why the answer is not "two weeks"
Ten business days from Tuesday 18 August 2026 is Tuesday 1 September 2026. Here the shortcut works: no federal holiday falls inside the span, so ten business days is exactly fourteen calendar days. Move the same question two weeks later and it stops working — ten business days from Tuesday 1 September 2026 runs past Labor Day on Monday 7 September, landing on Wednesday 16 September: fifteen calendar days rather than fourteen. "Ten business days" and "two weeks" are the same answer only in weeks that contain no holiday, which in the US is about forty-two weeks of the year — eleven of the 53 ISO weeks in 2026 contain one.
Where other business-day calculators disagree
- They count the start day. The most common single difference, and it produces an off-by-one on every answer. We do not count it; day 1 is the next business day.
- They skip the actual holiday, not the observed one. Independence Day 2026 falls on Saturday 4 July. The closure is Friday 3 July. A calculator skipping 4 July removes a day that was not a working day anyway and returns an answer one business day early.
- They use a different holiday list. Bank holidays, court holidays, state holidays and company holidays are four different lists. We use the eleven federal ones and name every one we skipped so you can check.
- They roll the answer forward off a weekend. Some legal-deadline calculators apply a second rule: if the computed date is not a working day, move to the next one. That rule belongs to a specific procedural code, not to arithmetic, so this page does not apply it — a business-day answer is already a working day by construction, but a calendar-day answer is not, and you may need that rule on top.
Counting backwards from a deadline
Enter a negative number to work backwards. This is the more useful direction for planning: given a filing date, when does preparation have to start? Ten business days before a deadline in the week after Thanksgiving is not the same as fourteen calendar days before it, and in that particular week the difference is two days rather than the usual four. The result names the holidays it stepped over in either direction. For the count between two dates you already have, use working days between two dates instead; for plain calendar arithmetic, the date calculator. The full business-day rule, including which weekend and whose holidays, is on the methodology page.