Week Number Calculator
Calculate the current week number, find week numbers for any date, and convert between dates and week numbers. Perfect for project planning, payroll, and scheduling.
Step 1: Select Date
About Week Number Systems
ISO 8601 is the international standard used in Europe and most of the world. US standard starts weeks on Sunday. UK traditional is similar to ISO but with different rules for week 1.
Step 2: Week Operations
Week Number Calculation
Week numbers help in business planning, project management, and payroll systems. Different countries and organizations use different week numbering systems.
Week Number Results
Week Number
Calendar View
Week Details
| Day | Date | Day of Year | Business Day |
|---|
Week Number Systems Comparison
| System | Week Start | Week 1 Contains | Week Number |
|---|
Week Calculation Formula
Week Number = ⌈(Day of Year + Offset) / 7⌉
Where Offset depends on the weekday of Jan 1 and the week numbering system used. ISO 8601: Week 1 is the week with the year’s first Thursday.
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