Week Number Calculator

What Week of the Year Is It?

This week number calculator shows the current week number instantly, plus the date range it covers. The most common standards are ISO 8601 (used internationally, with weeks starting on Monday) and the US system (with weeks starting on Sunday) — switch between them with the toggle. Your choice is remembered for next time.

Current Week Number

The week number depends on which standard you use. In ISO 8601, week 1 of the year is the week containing the first Thursday — used by most of Europe, including Germany, Scandinavia, and the Netherlands, where business planning by week numbers is standard practice. The US system numbers weeks consecutively from January 1, with week 1 always containing New Year's Day.

Calendar with Week Numbers

The full calendar by numbered weeks shows every week of the year with its start and end dates. The current week is highlighted automatically. Use the year selector to switch between past and future years — useful when planning sprints, scheduling deliveries, or filling in timesheets that ask for a week number rather than a date.

Why Week Numbers Matter

Many companies and tools track project timelines, payroll cycles, and production schedules by week number rather than by date. Engineering teams often plan sprints in numbered weeks (e.g., "we'll ship by W42"). Even if you only need to answer the simple question of what calendar week is it, the answer depends on which standard you follow — this tool makes both available side by side.

Related Tools

To count the days between two dates, use the Days Between Dates calculator. To add or subtract days from a given date, see the Date Calculator.