Week Number Calculator
Find the ISO week number of any date (and the US week number). Free online week number lookup.
✓ 100% free ✓ No sign up ✓ Runs in your browser — nothing uploaded
ISO week number
Week 45 of 2026
US week (Sunday start) Week 45
Date Monday, November 2, 2026
How to use Week Number Calculator
- 1Enter your numbers or dates.
- 2Results update instantly as you type.
- 3Copy the main result with one click.
Questions
Is Week Number Calculator free?
Yes. Week Number Calculator is 100% free with no limits, no watermark, no sign up and no email required.
Is my data sent anywhere?
No. Everything is calculated locally in your browser. Nothing you type is sent to or stored on any server.
Does Week Number Calculator work on my phone?
Yes. Week Number Calculator works in any modern browser on iPhone, Android, Windows, Mac, Linux and Chromebook. No app or install needed.
Do I need to create an account?
Never. There is no sign up, no login, no email and no paywall. Just open the page and use it.
How accurate is it?
Calculations use standard formulas with full floating-point precision. For medical, legal or financial decisions, please confirm with a professional.