Calendar · Date & Time
Week Number Calculator
Get the ISO week number and weekday for any calendar date.
ISO week
Week 30, 2026
Weekday
Tuesday
How to use
- Pick a date (defaults to today).
- Read the ISO week number and year.
- See which weekday it falls on.
Features
- ISO 8601 weeks
- Weekday name
- Runs in your browser. Dates stay on your device.
Privacy & how it works
This date and time tool runs in your browser. Dates and times you enter are not uploaded to ToolsWeb servers for this tool. Privacy Policy.
FAQ
What is an ISO week?expand_more
ISO 8601 week 1 is the week that contains the year’s first Thursday. Weeks run Monday–Sunday.
Is this calculator free?expand_more
Yes. No signup required.
Are my numbers uploaded?expand_more
No. Calculations run in your browser. Inputs are not sent to ToolsWeb servers for this tool.
Is this professional advice?expand_more
No. Results are estimates for general information. See our Disclaimer for health, finance, and related tools.