Business Days Calculator

The Kordu Business Days Calculator answers the two questions that almost every contract, invoice, SLA, and project plan eventually depends on: how many working days fall between two dates, and what date lands a given number of working days from today. It works in two modes and runs entirely in your browser — no signup, no uploads, no tracking.

What counts as a business day

For this tool, a business day is any weekday from Monday through Friday. Saturdays and Sundays are excluded. That convention matches the standard working week used across North America, the UK, most of the EU, Australia, and the majority of the Western commercial world. A few regions run a different weekend — historically Saudi Arabia, Iran, and parts of the Middle East use a Friday–Saturday weekend, while Israel uses Friday–Saturday — so if you're calculating for those jurisdictions you will need to shift the calculation manually. For everyone else, Mon–Fri is the commercial default and the one this calculator uses.

Why you can't just subtract dates

Calendar arithmetic lies to you about working time. Thirty calendar days from the 1st of a month lands on the 31st. Thirty business days from the same start date lands roughly six weeks later — because every weekend eats two days off the running total. Using a plain date difference for anything measured in working days (invoices, SLAs, delivery estimates, legal notices, onboarding timelines) silently overstates your budget and understates your deadline. A tool that counts only Mon–Fri days is the only way to convert between the two reliably.

Inclusive vs exclusive counting

This calculator uses the inclusive convention: both the start date and the end date are counted if they fall on a weekday. That matches how commercial contracts, procurement rules, court filing deadlines, and most SLA clauses are drafted in English-language jurisdictions. Some systems use exclusive counting ("30 business days after the invoice date, not counting the invoice date itself") — if your contract uses that wording, subtract one from the result. Always read the specific clause. Edge cases: if your start date lands on a Saturday or Sunday, it is skipped over in the count because it isn't a business day to begin with. Some legal systems formally roll such a start date forward to the next Monday before counting; the result is the same for count mode but matters in add mode.

Net-30, net-60, net-90 invoicing

The most common use for this tool is payment terms. "Net 30" in a B2B invoice typically means 30 days from the invoice date — but whether those are calendar days or business days depends on the jurisdiction and the contract. If your terms read "30 business days," switch to add mode, enter the invoice date, and add 30 to find the due date. That will be roughly six calendar weeks out, not four. Net-60 and net-90 follow the same pattern. Always check the master services agreement: some contracts are calendar days, some are business days, and mixing them up is the single most common AP dispute.

SLAs and response time commitments

Service-level agreements almost always quote response and resolution times in business hours or business days, not calendar days. A "two business-day response" on a Tuesday request lands on Thursday, not Wednesday (because the start day is inclusive in most SLA contracts — check yours). A five business-day resolution for a ticket opened on Friday is the following Friday, since the weekend drops out. Feed your SLA clock into add mode to get the exact due date rather than eyeballing it on a calendar.

Delivery windows and fulfilment estimates

Carrier and marketplace delivery estimates ("5–7 business days," "2–3 business days") are almost always business days. Five to seven business days is roughly one to one-and-a-half calendar weeks, depending on where the weekend falls. Use count mode to work backwards from a promised date, or add mode to see when a customer will realistically receive an order.

Legal notice periods and regulatory deadlines

Statutory notice periods — contract termination windows, GDPR breach notifications (72 hours), data subject request deadlines (one month under Article 12 GDPR, typically computed in calendar days), court filing cut-offs, tenancy notice, employment termination — are often measured in business days. Court rules in particular tend to count working days inclusively and roll deadlines forward when they land on a weekend or public holiday. This tool gives you the Mon–Fri count; you still need to consult the relevant rules of procedure for holiday roll-forward and the exact inclusive/exclusive convention.

Public holidays — the tool does not handle them automatically

This is the most important caveat. The calculator counts weekdays only; it does not subtract public holidays. Holiday calendars vary wildly: the United States has roughly 11 federal holidays plus state bank holidays, the United Kingdom has around 8 bank holidays in England & Wales (different in Scotland and Northern Ireland), each EU member state maintains its own list of 12–15 national holidays, and religious holidays (Eid, Diwali, Rosh Hashanah, Good Friday) shift each year by the lunar or ecclesiastical calendar. No client-side tool can reliably cover every jurisdiction and year without bundling a megabyte of data that will be stale within months. The practical workflow is: use this tool to get the raw Mon–Fri count, then subtract the holidays that fall inside your range by hand. For most countries you can look them up on gov.uk, the US Office of Personnel Management site, the official national gazette, or a maintained source like date-holidays on npm.

Trading days vs banking days vs business days

These are not quite the same thing. Trading days refer specifically to days when a given exchange is open — the NYSE, for example, closes on Good Friday even though it is a regular business day in most offices. Banking days are the days when interbank settlement runs; wire transfers, ACH cut-offs, and FX settlement all use this calendar and it includes additional closures like Juneteenth. For contractual purposes most commercial agreements define business days explicitly — read the definitions clause. If the contract silently says "business days," it usually means the national banking calendar of the governing jurisdiction.

Half-day holidays and early closes

Christmas Eve, New Year's Eve, and in some countries Maundy Thursday are treated as half-days by banks and many offices. The calculator treats them as normal business days — real-world handling depends on your industry. For SLA purposes, half-days are almost always counted as full days; for payment settlement, they often trigger the next-day rule.

Common mistakes this calculator helps you avoid

1. Treating a "30-day" contract clause as calendar when it says business days — that shortens your window by about two weeks.
2. Forgetting the inclusive rule and being off by one on every deadline.
3. Adding business days manually on a calendar and miscounting when the range crosses a month boundary.
4. Using calendar days for SLA reporting and then arguing with the counterparty about which one the contract meant.

Privacy and data processing

All calculations run client-side in your browser. Your dates and the numbers you enter are never sent to a server, logged, or stored. The tool works offline once the page has loaded, has no signup, and no rate limits. Pair it with the Kordu Date Difference tool when you need calendar-day results, the Week Number Calculator for ISO 8601 week numbers, or the Timezone Converter when the dates span multiple offices.