Counting Business Days: Deadlines, SLAs and Leave That Add Up
“We’ll get back to you within 10 business days” sounds precise. In practice it’s a small minefield: weekends, public holidays and the question of whether you count today all change the answer. Here’s how to count working days correctly — and avoid the arguments that follow when people count differently.
Business days vs. calendar days
A calendar day is every day on the calendar. A business day (or working day) is usually Monday to Friday, excluding weekends — and, depending on context, public holidays. The gap between the two is bigger than people expect: ten business days is two full weeks, and with a holiday in the mix it can stretch past a fortnight on the calendar.
The three things that trip people up
1. Weekends. Five working days from Thursday isn’t the following Thursday — it lands on the next Thursday once you skip the weekend in between.
2. Holidays. These are the silent killer of estimates, and they’re local: a date that’s a holiday in the US may be an ordinary workday in Germany. Because there’s no universal list, you have to supply the holidays that apply to you. The Working Days Calculator lets you paste your own holiday dates and subtracts any that fall on a working day.
3. Inclusive vs. exclusive counting. Does the clock start today or tomorrow? Does the deadline day itself count? Define this up front — for leave requests and project durations you usually want both endpoints included; for “within X days” deadlines you usually don’t.
A worked example
Say a refund is promised “within 5 business days,” starting Monday with no holidays that week:
- Day 1: Tuesday
- Day 2: Wednesday
- Day 3: Thursday
- Day 4: Friday
- Day 5: Monday (the weekend doesn’t count)
So a Monday request resolves the following Monday — eight calendar days later. Add one public holiday and it slips to Tuesday.
Where it matters most
- SLAs and support — “response within 2 business days” needs an agreed definition.
- Payroll and leave — annual leave is counted in working days, and getting it wrong costs real money.
- Contracts and notice periods — “30 working days’ notice” can vary by weeks depending on holidays.
- Shipping — couriers quote business days and skip non-delivery days.
Counting both ways
When you need the raw gap including weekends — trip lengths, age in days, anniversaries — use the Days Between Dates calculator. When you need only the days people actually work, switch to the Working Days Calculator. Pick the right one and your estimates stop being a source of friction.
Agree on the rules, count the weekends and holidays out, and “ten business days” finally means the same thing to everyone.