Working Days Formula Explained, With Examples
Every working days result comes from one formula. Once you understand what goes into it, you can sanity-check any figure you are given, whether by an employer, a bank, a teacher or another website.
The formula
Count Monday to Friday dates in the range.
What each input means
- Start date: the value you enter in the calculator.
- End date: the value you enter in the calculator.
Example
For example, with these inputs:
- Start date: 1 Oct 2026
- End date: 31 Oct 2026
the calculator returns:
- Weekdays (Mon–Fri): 22 days
- Calendar days: 31 days
Why it matters
Dates and durations matter for notice periods, leave planning, project deadlines and contracts. Counting days on a calendar is slow and easy to get wrong, especially across months of different lengths.
The Gregorian calendar has months of 28 to 31 days and adds a leap day almost every four years, which makes counting days by hand surprisingly error-prone. Converting dates to day numbers and subtracting avoids the problem.
When sharing dates internationally, write the month as a word to avoid confusion between day-month and month-day formats.
Singapore has 11 gazetted public holidays a year, and when one falls on a Sunday the following Monday is a holiday. Working-day calculations therefore need holidays removed separately from weekends.
Related calculations
- Age Calculator: Calculates exact age in years, months and days.
- Days Between Dates Calculator: Counts days between two dates.
- Add Days to a Date Calculator: Finds the date a number of days after another date.
- Subtract Days from a Date Calculator: Finds the date a number of days before another date.
Use the Working Days Calculator to plug in your own numbers.
Run your own numbers: Working Days Calculator