Week Number Calculator

Find what week of the year any date falls in

Find the ISO week number for any calendar date

Use this tool to check week-of-year references for planning, reporting, scheduling, payroll, or timeline coordination.

Date

Pick a date to calculate its ISO week number.

ISO week number

Choose a date and click Calculate.

The week number and Monday-to-Sunday range will appear here.

Check the current week number instantly

ISO week (Monday-Sunday)

— ISO week year

Not calculated yet Week range

— Selected weekday

— ISO week code

Choose the calendar date you want to check.
Click Calculate to see the ISO week number right away.
Review the ISO week year, weekday, and full week range in the result card.
Use Today for the current date or Use Example to load a sample calculation.

What week is March 1, 2026?
What is the current week number?
Check which ISO week a payroll cutoff date falls in.
Confirm the week number for a project deadline or reporting milestone.
See the Monday-to-Sunday range for a date used in a schedule or weekly recap.

This tool tells you which ISO week of the year a selected date belongs to. It also shows the ISO week year, the weekday of the selected date, and the full Monday-to-Sunday range for that week.

A week number calculator is useful when your planning, reporting, logistics, payroll, or project tracking process uses week-based references instead of only calendar dates. It helps when you need to map a specific date to its week-of-year label without checking a separate calendar table.

ISO weeks start on Monday and end on Sunday. The ISO week year can differ from the calendar year for dates near the start or end of January and December, which is why a dedicated ISO week calculation is often more reliable than guessing from a wall calendar.

- What week number is this date? - Which ISO week is today? - What week of the year is a deadline in? - What dates are included in ISO week 12?

Does this tool use ISO week numbers?

Yes. The result uses ISO week rules, where weeks run from Monday to Sunday and the ISO week year can differ from the calendar year near year boundaries.

Can the ISO week year be different from the calendar year?

Yes. Dates near the start of January or end of December can belong to an ISO week year that is different from the visible calendar year.

What is the current week number?

Use the calculator with today's date to see the current ISO week number.

Does the result show the full week range?

Yes. The result includes the Monday start date and Sunday end date for the ISO week that contains your selected date.

Week Number Calculator