How to Calculate Working Days: A Step-by-Step Guide

Updated 5 Oct 2026 in Date & Time

Counts weekdays between two dates, inclusive. Subtract any public holidays that fall on a weekday.

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.

What you need

• Start date
• End date

Step by step

1. Enter the start date.
2. Enter the end date.
3. The results update as you type, or press Calculate.
4. Read the weekdays (mon–fri) first, then the supporting figures below it.

The formula

Count Monday to Friday dates in the range.

Worked 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

Practical tips

• Notice periods in employment contracts may be counted in calendar days or working days, so read the wording carefully.
• Decide upfront whether the end date should be counted, because it changes the answer by one day.
• Public holidays are not weekends; subtract them separately when counting working days.
• For overnight shifts, add 24 hours when the end time is earlier than the start time.

Background

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.

Age is calculated in completed years, months and days. Someone born on 29 February is usually treated as turning a year older on 28 February or 1 March in non-leap years, depending on the rule being applied.

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.

Want to skip the arithmetic? The free Working Days Calculator does all of this instantly and updates as you type.

Run your own numbers: Working Days Calculator