Calculate dates by adding or subtracting weeks, find weeks between two dates, and get ISO week numbers
This week calculator helps you work with weeks in two ways: add or subtract a number of weeks from a date to find a new date, or calculate how many weeks lie between two dates. It also displays the ISO week number for every date shown.
For adding/subtracting weeks, enter a start date, the number of weeks, and choose forward or backward. For calculating weeks between dates, simply enter a start and end date. The calculator will handle both calculations at once and show ISO week numbers.
ISO 8601 defines week numbers starting from 1 for the first week of the year that contains a Thursday. Weeks run Monday through Sunday. The ISO week number is commonly used in business and European date systems.
The calculator divides the total number of days between two dates by 7. The result includes fractional weeks (e.g., 2.43 weeks) for precise measurement. The calculation uses absolute difference, so order of dates does not matter.