FREE · TIME & DATE TOOLS
ISO Week Calculator.
Find the ISO week number, week-year and weekday of a Gregorian date.
How to use ISO Week Calculator
Choose the operation, enter the required values and generate the result. Review units, calendar rules and assumptions before using it.
How it works
Find the ISO week number, week-year and weekday of a Gregorian date. YYYY-MM-DD, years 0001–9999. ISO weeks start on Monday and can cross calendar-year boundaries.
Example
2021-01-01 → 2020-W53-5
Questions about ISO Week Calculator
Is ISO Week Calculator free, and do I need an account?
Yes. This tool is free to use in your browser without an account. Processing takes place on your device.
What are the limits and what should I check?
YYYY-MM-DD, years 0001–9999. ISO weeks start on Monday and can cross calendar-year boundaries. Review the result before using it in your work.
Is my input sent to a server?
Your input is processed in your browser and is not uploaded by this tool. Files and pasted text are cleared when the page is refreshed. Normal website requests are still required to load the page and its libraries. Read the privacy explanation.