Business Days Calculator

Find how many workdays fall between dates or determine the date you reach after adding/subtracting business days, respecting weekends and holidays.

Calculation Mode

Weekend Days

How to Use This Calculator

Choose whether you want to count workdays between two dates or jump forward/backward by a specified number of business days. Configure weekends and holidays so the output matches your team's calendar.

  1. Select the calculation mode that matches your question (count between dates or add/subtract workdays).
  2. Enter the start date and, when counting, the end date. If adding/subtracting, fill in the number of days plus add/subtract direction.
  3. Toggle "Include Start Date" if you want the start day to count when it is a business day.
  4. Mark every weekend day that should be excluded from the count (default is Saturday + Sunday).
  5. List special holidays or closures, one per line in YYYY-MM-DD format, so they are removed from the business day total.
  6. Click Calculate to update the sticky results card. The primary metric and KPI rows refresh automatically.

Methodology

The engine walks day-by-day through your range, skipping weekend days and holidays as defined in the form. When counting between two dates, the end date is always evaluated, and the start date is optionally included. When adding or subtracting, the loop continues until the requested number of business days is reached while tracking how many weekends and holidays were skipped.
BusinessDays = \(\sum_{d = \text{DateStart} + 1}^{\text{DateEnd}} \begin{cases}0 & \text{if } d \in \text{Weekends} \\ 0 & \text{if } d \in \text{Holidays} \\ 1 & \text{otherwise} \end{cases}\)

Why use this calculator

  • Get instant, accurate workday counts for planning deadlines or SLAs.
  • Find a target date when you need to add or subtract business days.
  • Customize the workweek for international or non-standard schedules.
  • Exclude specific holidays to mirror corporate or government closures.
Formulas

The calculator loops through each calendar day between the start and end date, flagging weekends and holidays before incrementing the business day tally.

Day-by-day logic

let d = DateStart
let count = 0
while count < N_days
  d = d + 1 day
  if d not in Weekends and d not in Holidays
    count = count + 1
return d
Citations
Changelog
  • 0.1.0-draft — 2026-01-19: Initial audit spec draft generated from HTML extraction (review required).
  • Verify formulas match the calculator engine and convert any text-only formulas to LaTeX.
  • Confirm sources are authoritative and relevant to the calculator methodology.
Verified by Ugo Candido Last updated 2026-01-19 Version 0.1.0-draft
Formulas
Version 1.5.0