A free online week number calculator. Enter any date to get its ISO week number, day-of-year count, quarter, days remaining in the year, weekday name, and total weeks in that year. Includes a visual monthly calendar with the selected date highlighted. Perfect for project scheduling, payroll cycle planning, academic timetables, manufacturing production weeks, and ISO 8601 compliance — all computed locally in your browser.
Select a date using the date picker.
View the ISO week number and ISO year instantly.
See the day of year, days remaining, quarter, and weekday name.
Use the monthly calendar reference to visualize the date context.
ISO 8601 defines week numbers where week 1 is the week containing the first Thursday of the year. Weeks start on Monday, and each week belongs to the year that contains its Thursday.
Most years have 52 weeks, but about every 5-6 years, a year has 53 ISO weeks (e.g., 2020 had 53 weeks). The tool shows the exact week count for the selected year.
Free online tool — works in your browser, no sign-up required. Start using it right now.
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