The Conception Calculator

Born on August 20? Here's When You Were Conceived

Birthdays & conception. Updated . Calculated with the standard pregnancy dating method used by ACOG and the NHS.

If you were born on August 20 and arrived close to your due date, you were most likely conceived around November 27 the year before, in the autumn (northern hemisphere).

Conception estimates for a August 20 birthday

Born at 37 weeks (early term)December 18
Born at 40 weeks (on the due date)November 27
Born at 42 weeks (late)November 13
Most likely conception rangeNovember 13 – December 18
Mother's probable due dateclose to August 20 if born at full term

How the estimate works

A full-term pregnancy lasts about 266 days from conception to birth, or 280 days when counted from the first day of the mother's last period. Subtracting 266 days from a birth date gives the most likely conception day, assuming the baby was born around the due date.

If you were born early, conception was later than November 27; if you were born after your due date, it was earlier. A baby born two weeks early was probably conceived around December 18, while one born two weeks late was probably conceived around November 13.

Getting a more exact answer

If your parents know how many weeks pregnant your mother was when you were born, you can narrow this down. Each week earlier than 40 moves the conception date one week later, and each week past 40 moves it one week earlier.

You can also enter a full date of birth, with the year, into the conception calculator by birth date to get weekdays and the right year.

Conception Calculator by Birth Date: Estimate when someone was conceived from their date of birth.

Open the calculator

This article is general information, not medical advice. Talk to a doctor or midwife about your own pregnancy or fertility.