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Pregnancy Countdown Calculator

Enter how many days pregnant you are to see the countdown to your due date.

How it is calculated

The only input is how many days pregnant you are today, counted from the first day of the last menstrual period. The tool subtracts it from the standard full-term length of 280 days (40 weeks): days remaining = 280 − days pregnant, and then converts to weeks with weeks remaining = days remaining ÷ 7, shown with one decimal. Once you reach or pass 280 days the result stays at 0 rather than going negative. Values below 0 or above 310 are rejected and return no result. Weeks are a decimal, not weeks plus days: 4.3 weeks means about 4 weeks and 2 days. Only about 280 days is assumed; actual birth dates vary, and the figure is not a medical prediction.

Worked example

You are 250 days pregnant, which is 35 weeks and 5 days. Days remaining: 280 − 250 = 30. Weeks remaining: 30 ÷ 7 = 4.2857, shown as 4.3 weeks, that is 4 full weeks plus 2 days. So the estimated due date is 30 days from today. If you entered 280 or more, the result would show 0 days and 0.0 weeks.

Try this example →

Common mistakes

  • Entering weeks instead of days: typing 35 for 35 weeks gives 245 days left, because the field counts days.
  • Counting from conception or from the date of the positive test. The 280-day convention counts from the first day of the last period, about two weeks earlier.
  • Reading 4.3 weeks as 4 weeks and 3 days. The decimal is a fraction of a week: 0.3 week is about 2 days.
  • Treating the remaining days as a guaranteed birth date. It is a full-term convention; many babies arrive earlier or later.
  • Not updating the number as days pass, so an old entry shows a stale countdown.

Sources

About this calculator

This countdown works from the same 40-week (280-day) full-term convention used throughout obstetrics: given how many days pregnant you currently are, subtracting that from 280 gives the days remaining until the estimated due date, which can then be expressed in both days and weeks for easier tracking as the pregnancy progresses. It is simply the mirror image of a gestational-age calculation — counting down to the due date instead of counting up from the last menstrual period.

Expectant parents use a pregnancy countdown to track how much time is left in practical terms — for planning maternity leave, finishing nursery preparations, packing a hospital bag, or simply anticipation — since "37 weeks along" is harder to translate into a countdown than "21 days to go."

This calculator takes how many days pregnant you currently are and returns the days and weeks remaining until your due date.

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