NETWORKDAYS Working Days Formula

When planning construction milestones, software sprints, or production runs, calculating the exact time between two dates is critical. If you simply subtract dates (=FinishDate - StartDate), Excel counts every single calendar day, including Saturdays and Sundays when vendors, sub-contractors, and offices are closed.

This simple subtraction causes project managers to overestimate available production time and promise unrealistic delivery dates. To count only actual productive working days, Excel provides two specialized formulas: NETWORKDAYS and NETWORKDAYS.INTL.

Quick Comparison: NETWORKDAYS vs NETWORKDAYS.INTL

Both formulas calculate business days by removing non-working days. The difference is how much control you have over which days count as the weekend.

Core Formula Mechanics

1. Both Formulas Are Fully Inclusive

Unlike raw calendar subtraction, both NETWORKDAYS and NETWORKDAYS.INTL count both the start date and the end date if they fall on valid working days. For example, if a project starts on Monday and finishes on that exact same Monday, the formula returns 1 day, reflecting one full day of active work.

2. The Standard NETWORKDAYS Syntax

The standard formula requires a start date and an end date, with an optional range of public company holidays:

=NETWORKDAYS(start_date, end_date, [holidays])

If you have an official list of public holidays in cells $H$2:$H$10, simply pass that range as the third argument. Excel automatically checks whether each holiday falls on a weekday. If a holiday falls on a Saturday or Sunday, Excel ignores it so it is never deducted twice.

3. Customizing Weekends with NETWORKDAYS.INTL

For international operations or flexible work shifts, NETWORKDAYS.INTL allows you to define your own weekend pattern:

=NETWORKDAYS.INTL(start_date, end_date, [weekend], [holidays])

You can choose your weekend using pre-built number codes:

• 1: Saturday, Sunday (default standard)
• 7: Friday, Saturday (standard across the Middle East)
• 11: Sunday only (common for retail stores and factories operating 6 days a week)
• 12: Monday only

4. Advanced Custom Shifts with 7-Digit Strings

If your team works an irregular shift (such as taking Wednesdays and Thursdays off), you can pass a 7-character string of 0s and 1s representing Monday through Sunday ("MTWTFSS"). In this string, 1 marks a day off, and 0 marks a working day:

=NETWORKDAYS.INTL(B2, C2, "0011000") // Wednesday & Thursday off

Common Traps & How to Avoid Them

• Inverted Date Trap: If your start date is later than your end date, Excel returns a negative number. If you see unexpected negative numbers, verify your column references.
• Text Date Trap: If dates are stored as plain text with incompatible regional slashes, the formula returns #VALUE!. Wrap text inputs in DATEVALUE or convert them into true serial numbers first.
• Double-Deduction Worry: You do not need to manually filter out weekend holidays before supplying your holiday list. Excel checks this automatically.

Hands-on Practice Playground

Practice calculating net working days on the construction milestone schedule below. Complete each objective to verify your understanding.

In cell D2, calculate the standard business days for Foundation Pours between start date B2 and finish date C2.

In cell E2, calculate the business days for the same milestone assuming a Friday-Saturday weekend pattern (code 7).

In cell D3, calculate the standard working days for Steel Framing between B3 and C3.