Count business days
Business days are the weekdays in a period, counting both end dates. Any seven consecutive days contain exactly five, so the count is close to five sevenths of the calendar days. The remainder depends on which weekday the period starts. Monday 5 January 2026 to Friday the 16th is twelve calendar days and ten business days.
How to count business days
The starting weekday changes the answer more than people expect for short periods. Ten calendar days starting on a Monday contain eight weekdays; the same ten starting on a Saturday contain six. Over long periods the difference washes out to five sevenths, but for anything under a fortnight the start day matters and a rule-of-thumb multiplication will be wrong. The other thing worth pinning down is where day one sits. This page counts a span, both ends included, which is what a timesheet or a billing period means. A quoted turnaround usually counts differently: an SLA promising five working days from a Monday normally means the following Monday, because the clock starts on the next working day rather than the day the request arrived. Same five days, one day apart, and neither side is being difficult, which is why it is worth naming the target date rather than the count whenever the difference matters.
Questions
The weekdays inclusive of both ends, less any public holidays. Monday to Friday is five.
For short periods, considerably. Ten days from a Monday gives eight weekdays; from a Saturday, six.
Over months, yes — it is out by at most two days however long the span. Over a week or two, no.
Yes, which is the usual convention for a working-day count. An SLA that starts its clock on the next working day is one day different.
No. Only holidays landing Monday to Friday remove a working day. Where a substitute day is granted, count that instead.
This assumes Monday to Friday. Several countries take Friday and Saturday as the weekend, so adjust the figure yourself.
Because carriers usually exclude the despatch day as well as the weekends, and warehouse cut-off times push an afternoon order onto the next day.