Work Days Calculator

Working days exclude weekends and (typically) public holidays. Counting them between two dates gives realistic project timelines, payroll periods, and SLA windows. The naive calculation: (total_days × 5/7) minus holidays in the range — close enough for rough planning, exact-only when you walk the calendar.

Enter a start and end date plus a list of holiday dates to skip. Output is the count of working days in the inclusive or exclusive range. Default exclusions are Saturday and Sunday; some industries use different working weeks (Sunday–Thursday in parts of the Middle East).

The exact algorithm walks the calendar day by day, incrementing the count for each weekday not on the holiday list. The 5/7 approximation gets within a day or two for spans of a few weeks but drifts for longer ranges as the actual weekend distribution diverges from average. Holidays add another adjustment — about 10 federal holidays per year in the US, more in countries with religious or national observances. The formula approach: count business days in full weeks (number_of_weeks × 5), then add or subtract for partial weeks at the start and end based on which days fall where, then subtract any holidays in the range. The walk-the-calendar approach is slower but always exact.

A worked example. Project span: Monday June 1, 2026 to Friday June 26, 2026. Total days: 26 (inclusive). Weekends in range: June 6-7, 13-14, 20-21 = 6 days. Federal holiday: none in this range (Juneteenth June 19 falls on a Friday and is observed; subtract 1). Working days: 26 - 6 - 1 = 19. The 5/7 approximation: 26 × 5/7 = 18.6, off by less than 1. For longer ranges the approximation drifts further but stays within a few days. Standard SLA language ('5 business days') means 5 working days starting the next business day after receipt; counting the start day or not is contract-dependent and frequently disputed.

Limitations and convention questions worth noting. Holidays falling on weekends are handled differently by different employers. Federal employees in the US get the observed day off (Friday before or Monday after) when a holiday lands on a Saturday or Sunday. Some private employers follow this; some don't. Some payroll systems skip the actual date even when it's on a weekend. Decide once and apply consistently across the calendar. Half-days like Christmas Eve are usually treated as full work days unless explicitly listed; for project planning where partial days matter, count them as 0.5 manually. Bank holidays and public holidays overlap but aren't identical, especially internationally. UK bank holidays close banks but aren't always public holidays; US federal holidays close federal offices but private business closure varies. International work happens across non-Western work weeks: Saudi Arabia and several Gulf states moved from Sunday-Thursday to Saturday-Sunday weekends in 2021/2022. Israel runs Sunday-Thursday with Friday-Saturday off. Configure the calculator's weekend definition before counting if you're working with international vendors or remote teams under different regimes.