ISO Standard • Business Planning • Global Consistency

Week Number CalculatorFind Which ISO Week of the Year Any Date Falls In • International Business Standard

ISO Week Standard

Monday-Based Weeks

International Business

Select Date to Find ISO Week Number

Automatic calculation

Week numbers calculated using ISO standard (Monday-based weeks)

Quick Example Dates:

Monday Start

All weeks start on Monday, aligning with international business standards.

Year Boundary Logic

Weeks never split across years—a week belongs to the year containing its Thursday.

International Consistency

Same week numbers worldwide, essential for global business coordination.

Jan 1-7: Week 1*

Jun 30: ~Week 26

Dec 31: Week 1*

53-week years

*Depends on year boundaries per ISO rules

Select a Date

Choose any date to calculate its ISO week number and year progress

International standard • Business planning • Consistent worldwide

The ISO Week Standard: Why Businesses Need It