GlenCalc

Due date calculator

Choose how to date the pregnancy. You get the estimated due date, how far along you are on the date you pick, and when each trimester starts. Only about 1 in 20 babies arrives on the due date itself.

Your answer

Estimated due dateFriday, February 5, 2027
On October 31, 202626 weeks 1 day
Second trimester starts (week 14)Friday, July 31, 2026
Third trimester starts (week 28)Friday, November 6, 2026
Likely conceptionFriday, May 15, 2026
  • An estimate for general information, not medical advice. An early ultrasound gives the most accurate dating.

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How we worked it out

Updated as you change the numbers.

  1. Due date = last period + 280 days (Naegele’s rule).
  2. Weeks pregnant are counted from the first day of the last period (gestational age).

Method and assumptions

Pregnancy is dated from the first day of the last menstrual period: the due date is 280 days (40 weeks) later for a 28-day cycle, shifted by the difference for longer or shorter cycles. Conception usually happens about 14 days after the period starts, so the due date is 266 days after conception. For IVF, the transfer date plus 261 days (day-5 embryo) or 263 days (day-3) gives the same date.

Questions

If my last period started on May 1, 2026, when is my baby due?

Around Friday, February 5, 2027, with a 28-day cycle.

Sources

Method and figures checked on . Every worked answer on this page is covered by an automated test. Found a mistake? Tell us.

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