Coordinating across time zones with my UK and China colleagues means I’m constantly referencing week numbers. “Let’s sync up in Week 21” makes way more sense than saying “the week of May 19th” when you’re planning months ahead. Week Number puts this information exactly where I need it - right in my menu bar.
The app does one thing perfectly: displays the current ISO 8601 week number. On my Mac Mini M4, it shows up as “Week 20” in the menu bar, updating automatically as weeks roll over. You can add a customizable prefix if you want, though I keep mine simple. Click the menu bar item and you get a small window where you can look up week numbers for any date - surprisingly useful when planning quarterly reviews or sprint cycles.
What I appreciate most is the intentional simplicity. Sindre Sorhus deliberately kept this focused rather than adding fiscal week numbering or custom work week configurations. It follows your system settings for week numbering (ISO 8601 or Gregorian), which means it just works without configuration.
The app includes widget support, so I have the week number visible on my desktop and in Notification Center. This has become surprisingly valuable during remote stand-ups - I can quickly reference which week we’re discussing without context switching.
One minor consideration: if your organization uses fiscal weeks or non-standard week numbering systems, this app won’t help. It sticks to standard week numbering, which works perfectly for international coordination but might not match your company’s internal calendar system.
Week Number runs on macOS 15 or later, with version 1.1.0 available for macOS 14. Memory footprint is negligible - around 30MB - and CPU usage is essentially zero since it only updates once per week. The app is completely free, which feels generous for something I use daily.
After a month of having week numbers readily accessible, I’ve noticed my team references them more often in planning conversations. It’s become our shared temporal language, and Week Number makes that effortless. For anyone working in environments where week-based planning matters, this tiny utility is surprisingly essential.
