Weeks Calculator

What Is a Weeks Calculator?

A weeks calculator converts between weeks and other time units, calculates the number of weeks between two dates, or finds a date a specified number of weeks in the future or past. How many weeks until summer vacation? How many weeks pregnant are you? What date is 12 weeks from today? Enter your dates or values in the calculator above for instant conversion between weeks, days, months, hours, and minutes with precise results for any time span.

Weeks to Days and Other Conversions

1 week = 7 days = 168 hours = 10,080 minutes = 604,800 seconds. 2 weeks = 14 days (a fortnight). 4 weeks = 28 days (not exactly 1 month). 13 weeks = 91 days (approximately 1 quarter). 26 weeks = 182 days (approximately 6 months). 52 weeks = 364 days (1 day short of a year). A common source of confusion: 4 weeks is not equal to 1 month because months have 28-31 days. Similarly, 52 weeks is not exactly 1 year because 52 times 7 = 364, one day short. This one-day discrepancy is why the same date falls on a different day of the week each year in a regular year and shifts by two days in a leap year.

Weeks in Pregnancy

Pregnancy is measured in weeks from the first day of the last menstrual period (LMP), totaling approximately 40 weeks (280 days). First trimester: weeks 1-12. Second trimester: weeks 13-26. Third trimester: weeks 27-40. Each prenatal visit tracks progress by week number, and developmental milestones are referenced by gestational week. Enter your LMP date to calculate your current week of pregnancy, estimated due date, and trimester. Premature birth is defined as before 37 weeks. Full term is 39-40 weeks. Post-term is beyond 42 weeks. These weekly benchmarks guide medical decisions throughout the entire pregnancy journey.

Weeks in Business and Project Management

Project timelines are frequently planned in weeks. A 12-week product development sprint. A 6-week marketing campaign. An 8-week training program. A 52-week rolling forecast. Agile software development uses 1-2 week sprints as the fundamental planning unit. Academic semesters are typically 15-16 weeks. Corporate quarters are 13 weeks. Fiscal years are 52 or 53 weeks (the 53-week year occurs roughly every 5-6 years in retail 4-4-5 calendar systems). Planning in weeks provides more granularity than months while remaining practical for scheduling meetings, milestones, and deliverables across team calendars.

How Many Weeks Between Two Dates?

Divide the number of days between two dates by 7. From January 1 to April 1 (90 days in a non-leap year): 90 / 7 = 12 weeks and 6 days. The calculator shows both the exact number of complete weeks and the remaining days. For business planning, partial weeks are often rounded up (a task spanning 12 weeks and 6 days is planned as 13 weeks). For pregnancy tracking, partial weeks are typically expressed as "12 weeks and 6 days" or "12+6" in standard medical notation used by obstetricians and midwives worldwide.

Weekly Patterns and Schedules

Many recurring activities follow weekly cycles. Payroll is processed weekly or biweekly (every 2 weeks). Biweekly pay results in 26 paychecks per year, not 24 (which would be semi-monthly). Mortgage payments can be set to biweekly, resulting in 26 half-payments per year, equivalent to 13 full monthly payments instead of 12, which pays off the loan faster and saves substantial interest. Weekly grocery spending, exercise schedules, medication dosing, and appointment scheduling all benefit from thinking in weeks rather than months because weeks are perfectly consistent at 7 days while months vary from 28 to 31.

Converting Weeks to Months

Because months have different lengths, the weeks-to-months conversion is approximate. 4 weeks = 28 days (slightly less than any month). 4.33 weeks = average month (30.44 days / 7). Common approximations: 6 weeks = about 1.5 months. 8 weeks = about 2 months. 12 weeks = about 3 months. 16 weeks = about 4 months. 20 weeks = about 5 months. For precise conversions, use exact dates rather than approximate month equivalents. The calculator provides both week counts and equivalent month-and-day breakdowns for any date range you need to analyze or communicate to others. This dual display eliminates the ambiguity that arises when different people interpret week-to-month conversions differently.

Frequently asked questions