Week Number Calculator
Get the ISO 8601 week number and week-year for any date, with the Monday-to-Sunday range of that week.
Runs in your browserDate → ISO week
Loading tool…
Example
2024-03-15
Week 11 (2024-W11), Monday 2024-03-11 to Sunday 2024-03-17
How to use the Week Number Calculator
- Paste or type your Date into the input area, or open a file from your device.
- Adjust the options above the editor if the tool offers any.
- Review the ISO week result, then copy it or download it as a file.
Privacy and limitations
- Your data is processed on your device and is not uploaded to any server.
Frequently asked questions
Why is 30 December 2024 in week 1 of 2025?
ISO weeks start on Monday and week 1 is the week containing the year’s first Thursday, so a few days near New Year belong to the neighbouring week-year.
Related converters
Day of the Week CalculatorFind which day of the week any date falls on, past or future, for one date or a whole list.ISO 8601 Date ConverterConvert dates or timestamps to ISO 8601 extended, basic, week-date and ordinal-date forms at any UTC offset.Seconds to Time ConverterConvert a number of seconds to HH:MM:SS, compact 1h 2m 3s, or words like "1 hour, 2 minutes and 3 seconds".Time to Seconds ConverterConvert durations like 01:30:00, 90:00, 1h 30m or "2 hours 15 minutes" to seconds, minutes or hours.Cron Expression ParserExplain a 5-field cron expression in plain English and list its next run times in UTC.Time Zone ConverterConvert a date and time between any two IANA time zones with daylight saving time handled automatically.Age CalculatorCalculate exact age in years, months and days from a date of birth, plus total days and the next birthday.Date Add / Subtract CalculatorAdd or subtract years, months, weeks, days and hours from a date, with correct month-end handling.