Week Calculator
Find the exact weeks and days between any two dates with this free online week calculator. Get ISO week numbers, day of week info, charts, and breakdowns.
About This Calculator
The Week Calculator helps you find the exact number of weeks and days between any two dates. Whether you are planning a project timeline, tracking pregnancy weeks, counting down to an event, or scheduling work sprints, this tool provides precise week-level and day-level calculations instantly.
To calculate weeks between dates, the calculator counts the total days from the start date to the end date (excluding the start date), then divides by 7. The result shows full weeks plus any remaining days. In addition, the calculator displays the ISO 8601 week number and day of the week for both dates, giving you complete temporal context.
How the formula works: Total days between dates = End date - Start date. Full weeks = floor(total days / 7). Remaining days = total days % 7. ISO week numbers follow the standard where Monday is day 1, and week 1 contains the year's first Thursday.
Regional Notes
India (IN): The Indian work week typically runs Monday to Friday with Saturday as a half-day in many sectors. The ISO week number standard is commonly used in corporate and IT planning.
United States (US): The US work week generally runs Monday to Friday, though many calendars consider Sunday the first day of the week. US project planners often use week-of-year numbering starting from January 1 rather than ISO standard.
United Kingdom (UK): The UK follows the ISO 8601 standard with Monday as the first day of the week. Week numbers are widely used in government, education, and business planning across the UK.
Frequently Asked Questions
How do I calculate weeks between two dates?
To calculate weeks between two dates, count the total number of days between them, then divide by 7. The whole number is the full weeks, and the remainder is the extra days. Our calculator does this instantly — just enter your start and end dates.
How many weeks are in a year?
A common year has 52 weeks plus 1 day (365 days), while a leap year has 52 weeks plus 2 days (366 days). Most years have 52 ISO weeks, but some years have 53 weeks depending on when the year starts.
What is ISO week numbering?
ISO 8601 week numbering defines Monday as the first day of the week. Week 1 is the week containing the first Thursday of the year. Week numbers range from 1 to 53, and week 1 may start in late December of the previous year.
Is the start date included in the week count?
By default, the start date is not counted in the week calculation. The calculator counts full days between the start and end dates. For example, from Monday to the following Monday is exactly 7 days or 1 week.
Can this week calculator help with project planning?
Yes, this week calculator is excellent for project planning. Use it to determine the number of weeks between project start and end dates, track sprint durations, plan delivery timelines, and schedule milestones with precise week-level granularity.
What is the first day of the week in different countries?
ISO 8601 designates Monday as the first day of the business week. However, the US, Canada, and many Asian countries consider Sunday the first day, while some Middle Eastern countries begin with Saturday. Our calculator follows the ISO standard for week numbers.