How to calculate business hours between two dates and times

A deadline expressed in business hours cannot be calculated as a simple difference between two timestamps. From Friday at 16:00 to Monday at 10:00, many calendar hours pass but only a few fall inside normal office hours.

Business day, business hour and worked hour

A business day is a day included in the working calendar, typically Monday to Friday in Bethemesh’s generic calculation. A business hour is time inside a defined opening window, such as 09:00–17:00. A worked hour is time actually worked by a person, possibly after subtracting breaks.

Use the business hours calculator for available opening time and the work hours calculator for an individual’s net working time.

Example across several days

For a period from Thursday 15:00 to Monday 11:00 with opening hours 09:00–17:00, Monday to Friday: Thursday contributes 2 hours, Friday 8, Saturday and Sunday 0, and Monday 2. Total: 12 business hours.

Counting business days alone is not enough when start and end times matter. Business-hour calculations are useful for support windows, processing deadlines, service availability and operational periods crossing a weekend.

Holidays and exceptions

A generic Monday-to-Friday calculation does not automatically represent every real business calendar. Public holidays, exceptional closures and organization-specific non-working days may need separate handling. Bethemesh deliberately separates technical calculation from legal or contractual rules.

A reliable manual method is to identify included days, remove non-business days, clip each remaining day to opening hours and add the durations. The calculator automates those steps locally in your browser.