Calculator
How to work out the weeks between two dates
The calculator finds the number of days between your two dates and divides by 7. You see the answer two ways: as whole weeks and leftover days, which is how most people say it, and as a decimal number of weeks for spreadsheets and reports.
weeks = total days ÷ 7Worked examples
- 1 January 2026 to 1 July 2026 is 181 days, which is 25 weeks and 6 days (25.86 weeks).
- A normal year is 365 days, or 52 weeks and 1 day. A leap year is 52 weeks and 2 days.
- 12 weeks is exactly 84 days. To find the date 12 weeks from today, use the Add or Subtract Days from a Date.
What is an ISO week number?
Many calendars, payroll systems and project plans refer to “week 27” rather than a date. The ISO 8601 standard defines it: weeks start on Monday, and week 1 is the week that contains the first Thursday of the year. That means the first days of January can belong to week 52 or 53 of the previous year, and the last days of December can belong to week 1 of the next. The calculator shows the ISO week for both of your dates. For example, 31 December 2026 falls in week 53 of 2026.
Everything is calculated in your browser. The dates you enter are never uploaded or stored on our servers; they only appear in a link if you choose “Copy link to this result”.
Where week counts are useful
- Project and sprint planning: how many weeks between kickoff and launch.
- Notice periods, courses and training programmes: these are often written in weeks.
- Countdowns: weeks until an event, holiday or exam.
- Working time: if you need working days rather than calendar weeks, use the Business Days Calculator. For an exact day count, use the Days Between Dates Calculator.
Frequently asked questions
How many weeks are there between two dates?
Count the days between them and divide by 7. The result shows both whole weeks plus leftover days and the decimal figure.
How many weeks are in a year?
A normal year has 52 weeks and 1 day, and a leap year has 52 weeks and 2 days. Under the ISO system a year has either 52 or 53 numbered weeks.
What is the difference between ISO weeks and simple weeks?
Simple weeks just divide days by 7. ISO weeks are the numbered weeks of the calendar year, starting on Monday, and are used in many business systems.
Does it include the end date?
Not by default. Tick “Include the end date” to count both the first and the last day.
Can I count working weeks?
Yes. The Business Days Calculator shows the working days between two dates and the equivalent number of 5-day weeks.
More date & time calculators
- Date & Time Difference CalculatorThe exact gap between two dates and times, with time zones.
- Days Between Dates CalculatorCount the days between any two dates, with or without the end date.
- Business Days CalculatorWorking days between two dates, minus weekends and public holidays.
- Hours Between Times CalculatorHours worked between two times, with breaks, overnight shifts and decimal hours.
- Add or Subtract Days from a DateFind the date that is N days, weeks, months, years or business days away.
- Age CalculatorExact age in years, months and days, plus your next birthday.
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