Week Number Calculator
By Miikka · CalcBrew · Updated
Finland and Europe use ISO 8601 week numbering: the week starts on Monday and the first week of the year is the one containing the year's first Thursday.
This week number calculator quickly tells you which week is currently running or which week a given date falls in. Week numbers are widely used in business, logistics and across Europe to schedule work, school and projects.
How the calculator works and what it’s for▾
How the week number is determined
Europe and most business software follow the ISO 8601 standard, in which the week starts on Monday. The first week of the year is the one that contains the year's first Thursday.
Because of this, the opening days of a year can belong to the last week of the previous year, and some years have 53 weeks. The calculator handles this automatically, so you always get the correct number.
What you enter and what you get
You can check the number of the current week or enter any date you like. The calculator tells you which week it is.
It also works the other way around when you want to know which date range a particular week number covers in the calendar.
Why week numbers matter
Week numbers are part of everyday life in shift planning, agreeing on holidays, dividing the school year and setting project timelines. Many people refer to meetings by week number alone.
Keep in mind that not every country uses the European method, so in international work it is worth confirming which standard is being used.
🔄 Reviewed June 2026
Frequently asked questions
Cite this calculator
CalcBrew. (2026). Week Number Calculator. https://calcbrew.com/week-number-calculator“Week Number Calculator.” CalcBrew, 2026, calcbrew.com/week-number-calculator.Link to https://calcbrew.com/week-number-calculator. Results are estimates; cite the underlying formula or data source for academic work.
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