Week Number Calculator
Find ISO week number for a date.
Scratchpad (not saved)
Save to create a persistent, shareable workspace.
What This Calculator Does
Find ISO week number for a date.
It combines Year, Month, Day to estimate ISO Week Number.
Formula & Method
Core equations: ISO week via Thursday anchor: W=1+\left\lfloor\frac{DOY_{Thu}-1}{7}\right\rfloor.
Notation used in the formulas: R = ISO Week Number; x_{1} = Year; x_{2} = Month; x_{3} = Day.
Method summary: inputs are normalized to consistent units, core equations are evaluated, then secondary values are derived and rounded for display.
Use this calculator for quick scenario analysis. Start with baseline values, change one driver at a time, and compare how sensitive the results are to each input shown above.
Inputs Used
- Year: Used directly in the calculation.
- Month: Used directly in the calculation.
- Day: Used directly in the calculation.
Related Calculators
- Date Difference Calculator — Compute days, weeks, and approximate months between two dates.
- Add/Subtract Days Calculator — Find a future or past date by adding or subtracting days.
- Age Calculator — Calculate exact age from birth date to a reference date.
- Weekday Finder — Find the day of week for any calendar date.
- Work Days Calculator — Count business days between two dates excluding weekends.
- Time Zone Converter — Convert a time between UTC offsets.
- Unix Timestamp Calculator — Convert a date-time to Unix epoch seconds.
- Countdown Calculator — Count down days remaining until a target date.