Week Number Calculator

Find which week of the year a date falls in, based on ISO 8601.

When to use?

Use it to find which year and week a date belongs to — for sprints, weekly reports, or production schedules.

Pick or type the date you want to check.

The ISO week starts on Monday, with the week containing the first Thursday as week 1. The common week treats the week containing January 1 as week 1.

Organize weekly schedules - Quickly find the week number for a report or work plan.
Check sprint week - See which week of the year a development sprint falls in.
Production/logistics planning - Use a date's week number for weekly production planning.

The definition of the first week (week 1) can differ between the ISO 8601 basis and the common basis.
Time-zone settings can cause a one-day difference in some cases.

Yes. It shows both the ISO week and the common week based on January 1.

The ISO week starts on Monday with the first-Thursday week as week 1; the common week counts the week containing January 1 as week 1.

Usually 52, though some years have 53.

In ISO, a late-December date can be week 1 of the next year, and an early-January date the last week of the previous year.

Day of the Week Calculator - Find the day of the week for a date and its day difference from today.
Date Difference Calculator - Calculate the number of days between two dates, or the date N days from a reference date.
Date Range Generator - Generate a list of all dates between a start and end date at once.
D-Day Calculator - Show the days remaining until, or elapsed since, a target date based on today.
Age Calculator - Calculate your exact age, this year's birthday status, and days until your next birthday.
Time Calculator - Add or subtract time from a clock time, and calculate the interval between two times.