About Week Number Now

Week Number Now answers one simple question — what week is it? — and then goes further. It shows the current week number in both the international ISO 8601 system and the US Sunday-start system, the exact dates of this week, a countdown to the end of the week, and how far through the year we are.

What you can do here

• See today’s week number in large type, with copy-ready formats such as 2026-W43.
• Switch between ISO (Monday start) and US (Sunday start) numbering. Your choice is remembered on your device.
• Convert any date to its week number, or any week number to its dates.
• Browse and print a full-year table of week numbers for any year.
• Count the weeks and days between two dates.

How it works

Everything is calculated in your browser using your device’s own date, time and time zone. Nothing you type into the calculators is sent to a server. The week calculations follow the ISO 8601 rules (weeks start on Monday; week 1 contains the first Thursday of the year) and have been checked against a reference implementation for every day from 1970 to 2199.

Accuracy

We work hard to keep the calculations correct, but the site is provided for general information. For legal, payroll or contractual deadlines, please confirm dates with the official calendar your organization uses — some companies use their own fiscal-week systems.

Advertising

The site is free to use and is supported by advertising provided by Google AdSense. See our Privacy Policy for details about cookies.

Contact

Suggestions and corrections are welcome — please visit the Contact page.