4-Day / Custom Work Week
Calculate business days using any custom work-week pattern.
Written and maintained by Paul Clark, Redmoon Software · Rules last verified
These calculators are for informational purposes only and do not constitute legal, financial, or professional advice.
How the 4-Day / Custom Work Week works
The 4-Day / Custom Work Week calculator counts business days between two dates against a workweek that isn't necessarily Monday through Friday. Choose a standard non-standard preset — a four-day Monday-Thursday week, a Sunday-Thursday week common across much of the Middle East, or a Monday-Saturday retail calendar — or tick your own exact set of working weekdays in the checkboxes beneath it, and the count reflects that real pattern rather than assuming the default. Picking a preset ticks the matching boxes for you, so whatever is checked is always what gets counted.
A "business day" is only meaningful relative to the specific set of weekdays an organization actually works. Two teams counting "10 business days" from the same start date land on different calendar dates if one runs a standard five-day week and the other runs a four-day week, because the same number of working days takes longer to accumulate at four per week than at five.
Worked example
Twenty working days from a Monday spans exactly four calendar weeks on a standard Monday-Friday schedule, landing on a Friday. The same twenty working days on a Monday-Thursday 4-day week takes five calendar weeks to accumulate, landing a full week later — even though both are honestly "20 business days" from the identical start date.
Frequently asked questions
What non-standard workweeks are supported?
The preset dropdown offers four: the standard Monday-Friday week, a four-day week (Monday-Thursday), a Sunday-Thursday week, and a Monday-Saturday week. Choosing one ticks the matching weekday checkboxes, and you are free to adjust those boxes afterwards — any other pattern, a Sunday-Friday six-day week included, is built by ticking weekdays directly rather than picked from the list.
Can I use a completely custom set of working days?
Yes. If none of the presets match your real calendar — a restaurant closed Monday and Tuesday, for example — choose your exact working weekdays directly and the count is based on that specific set.
Does it still apply public holidays on top of the custom workweek?
Yes. Select the relevant country and its public holidays are excluded from the count in addition to whichever weekdays fall outside your chosen workweek.
What this calculator does not do
A limitation you know about costs far less than one you find after the deadline. These are the specific things this tool cannot work out for you.
- Where both a workweek preset and the individual day checkboxes are shown, the checkboxes govern. Changing the preset rewrites them so the two cannot silently disagree.
- A working day is whole. Fractional days and rostered days off are not modelled.
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