Week Number Calculator
Enter a date to find its ISO week number, ISO week-year, and exact Monday-to-Sunday range.
Continue with another calculation
Core Week Calculator
Convert dates to ISO weeks, turn week numbers into date ranges, calculate weeks between dates, add/subtract weeks and count from today.
Open →Planning Calculators
Plan deadlines, project timelines, payroll periods, work anniversaries and timesheet weeks.
Open →Week Calendar
Browse ISO weeks by year with Monday-to-Sunday ranges and highlighted current week.
Open →When to use this tool
Use this for a quick answer when you need to know which ISO week a date belongs to.
Practical uses
Enter a date to find its ISO week number, ISO week-year, and exact Monday-to-Sunday range.
These planning tools are designed for quick answers, but they also work well as part of a bigger workflow. You can pair them with the year calendar, current week page and week guides to plan projects, delivery windows, payroll cycles, reporting periods and deadlines.
FAQ
Does this use ISO weeks?
Yes. Weeks start on Monday and end on Sunday.
Can the week-year differ from the calendar year?
Yes. Dates near New Year can belong to the previous or next ISO year.