What is an ISO week date?

An ISO week date follows the ISO 8601 standard where weeks start on Monday and Week 1 is the week containing the first Thursday of the year.

Why do some years have 53 ISO weeks?

Certain years contain 53 ISO weeks when the year starts or ends near a Thursday according to ISO 8601 rules.

Can I convert ISO week numbers back to dates?

Yes, the ISO Week Date Converter can convert ISO year, week number, and weekday back into a standard calendar date.

Is the ISO Week Date Converter free?

Yes, it is completely free and works directly in your browser with no registration required.

ISO Week Date Converter – Convert Date to ISO Week Number (ISO 8601)

ISO Week Converter

Convert between Gregorian dates and ISO week dates (ISO 8601)

Gregorian → ISO week

Select date

ISO week: —

Weekday: —

ISO week → Gregorian

ISO Year Week number Weekday (1=Mon … 7=Sun)

Date: —

ISO weeks start on Monday. ISO week 01 is the week with the year's first Thursday (or Jan 4).

Used by project managers, developers, accountants, and planners worldwide, this ISO week counter helps calculate accurate ISO week numbers based on international standards.

ISO Week Counter – ISO Week Number Calculator

The ISO week counter is a free online tool that helps you find the ISO week number for any date instantly. It follows the ISO-8601 international date standard used in business, finance, project management, and software systems.

Whether you need the ISO week number now, an ISO week number calendar, or an ISO week counter from date, this tool delivers fast and reliable results.

What Is an ISO Week Number?

An ISO week number is part of the ISO-8601 standard, where each year is divided into numbered weeks. ISO weeks start on Monday and end on Sunday.

Week 1 is the week with the year’s first Thursday
ISO weeks always start on Monday
A year can have 52 or 53 ISO weeks

ISO Week Number Now

The ISO week number now feature shows the current week according to the ISO calendar, helping teams track schedules, deadlines, and weekly planning accurately.

ISO Week Calculator

The ISO week calculator allows you to select any date and instantly calculate its corresponding ISO week number.

Select or enter a date
The tool calculates the ISO week automatically
View the correct ISO week count instantly

ISO Week Counter by Date

With the ISO week counter by date, you can find the exact ISO week for any past, present, or future date. This is especially useful for reports, payroll, sprint planning, and compliance documentation.

ISO Week Number Calendar

An ISO week number calendar displays all ISO weeks for a given year, making it easy to see weekly breakdowns at a glance.

This tool also works as an ISO week counter calendar, helping you track week progression throughout the year.

ISO Week Number 2025

The ISO week number 2025 view helps you understand how weeks are structured for the year 2025 under the ISO-8601 standard. This is useful for long-term planning and yearly schedules.

ISO Week Counters & Use Cases

Project and sprint planning
Payroll and timesheets
Accounting and finance reports
Software development timelines
International business scheduling

These ISO week counters ensure consistent week calculations across regions and systems.

🔐 Accuracy, Standards & EEAT Compliance

Based on ISO-8601 international standard
No data is stored or tracked
Browser-based and instant calculation
Reliable for professional and business use

Start Using the ISO Week Counter

Quickly calculate ISO week numbers using the ISO week counter calculator.

Check ISO Week Number Now