A business day is whatever your contract says it is
There is no universal definition. A business day is a day your organisation, your bank or your contract treats as working, and the three do not always agree. The count this page produces is therefore not a fact about the calendar; it is the result of four choices you make, and the reason the calculator asks for all four rather than assuming them.
Business days = calendar days in the range − weekend days − public holidays on a weekday − your own non-working dates
Calendar days in the range counts both the first and last date by default, because that is how almost everyone reads “from Monday to Friday”. Turn that off and the count runs between the dates instead, which is how some contracts define a notice period. Weekend days are whichever days you nominate, not automatically Saturday and Sunday. Public holidays come from a dated list for the region you choose, and only count once — a holiday that already falls on a weekend is not subtracted twice. Your own non-working dates are the company shutdown, the factory fortnight, the local day nobody publishes.
The order matters. A weekend day is removed before the holiday check, so Christmas Day on a Saturday is counted as a weekend day and not as a holiday. That is why the holiday total on a long span is usually smaller than the number of holidays in the list, and it is the right behaviour: you were not going to work that day either way.
Where the holiday dates come from, and when we admit we have none
Holiday dates are the part of a business-day calculator that is easiest to get quietly wrong, because a wrong answer looks exactly like a right one. Nothing on this page is typed from memory. The United Kingdom regions use the dated list the UK government publishes as machine-readable data, retrieved on a stated date and covering stated years. The United States uses the federal holidays as the statute defines them — 5 U.S.C. § 6103 gives them as rules rather than dates, so “the fourth Thursday in November” is computed for whichever year you ask about and cannot go stale the way a copied list does.
The same statute carries the substitution rule, and the calculator applies it. Independence Day 2026 falls on a Saturday, so federal offices observe it on Friday 3 July; the tool removes the third, not the fourth. The UK data encodes its own substitutes the same way — Boxing Day 2026 is a Saturday, and the published list moves the holiday to Monday 28 December.
When you pick a region we do not hold, or a year outside the range a published list covers, the calculator says so in plain words and tells you the total excludes weekends but no holidays. It does not silently return a number as though there were no holidays that year. Currently supported: United States — federal holidays; United Kingdom — England & Wales; United Kingdom — Scotland; United Kingdom — Northern Ireland. For anywhere else, put the dates in the non-working field yourself — that is an honest count you control, rather than a confident one that happens to be wrong.
A quarter, counted
Take the last quarter of 2026 in England & Wales — 1 October to 31 December, inclusive of both. That is 92 calendar days. Of those, 26 fall on a Saturday or a Sunday, and 2 are bank holidays landing on a weekday: Christmas Day on 2026-12-25 and Boxing Day on 2026-12-28. What is left is 64 business days.
Notice what the arithmetic tells you that a calendar does not. A quarter that reads as three months of work is, once weekends and two bank holidays are removed, 64 days — and if your team also takes the working days between Christmas and New Year, you are planning against something closer to 61. Deadlines set by counting months are set against the 92; work gets done in the 64.
Those figures are produced by the same engine as the calculator above, from the same published holiday list, when this page is built. They cannot drift away from the tool.
Counting forward instead: the date forty-five business days out
Contracts, courts and service agreements rarely say “by 14 November”. They say “within 45 business days”, and someone has to turn that into a date. Switch the calculator to its second mode, give it a start date and a number, and it walks the calendar forward one day at a time, skipping every day your settings exclude, until it has counted the days you asked for. It reports how many non-working days it stepped over on the way, which is the number that explains why the answer is further out than it felt.
A negative number walks backwards, which is the more useful direction more often than people expect: given a filing date, it tells you the last day you can start. The two directions are exact inverses, and the test suite proves it over a hundred randomly generated spans rather than a couple of hand-picked ones.
The weekend is not Saturday and Sunday everywhere
Much of the Gulf works Sunday to Thursday, so the weekend is Friday and Saturday. Israel’s is Friday and Saturday. Nepal has a one-day weekend. A six-day working week with only Sunday off is normal across much of South Asia and in plenty of retail and manufacturing anywhere. A calculator that hardcodes Saturday and Sunday is not a business-day calculator; it is an American and European one.
So the weekend is a setting, and it applies to both modes. If you are counting a supplier’s turnaround in a country that works Sunday to Thursday, set it and the count changes accordingly. If your own operation runs six days, set Sunday only and the same span produces a larger number. Neither is more correct — they are different questions, and the tool should not answer one when you asked the other.
What this does not settle
This counts days. It does not know what your contract means by them, and that ambiguity is where most disputes actually live. “Within 10 business days” may or may not include the day the clock started, and the inclusive setting is there because your agreement decides that, not this page. A deadline expressed in business hours rather than days is a different calculation again — one that has to know when your working day starts and ends.
It cannot know about regional or local holidays below the level the published data covers, a holiday declared at short notice, or a day your own organisation closes. Those go in the non-working field. It does not model half-days, time zones, or a holiday that is observed by banks but not by courts — a distinction that matters in practice and is not in any dataset we could cite. And it is a planning tool, not legal advice: where a date carries a legal or contractual consequence, confirm it against the agreement and the relevant authority before relying on it.
Sources
Holiday dates: the published lists and statutes below, not our own compilation. Each region on the page names its own source, the years it covers, and when the data was retrieved.