Retroactive Pregnancy Calculator

With a standard 28-day cycle, ovulation occurs around day 14. So if your last period started February 12, you likely conceived around February 26 (14 days later), give or take 3 to 5 days. Your estimated due date would be November 19 (280 days from LMP). Enter your exact date above for a full timeline.

A July due date means conception likely occurred in October of the previous year. Due date July 1 = conception around October 8. Due date July 15 = conception around October 22. Due date July 31 = conception around November 7. The calculator above will give you the exact dates plus trimester ranges.

Yes. Select "Baby's Birth Date" from the dropdown and enter the date. The calculator subtracts 266 days to estimate conception. This assumes a full-term delivery. If your baby was born early or late, adjust the estimate: subtract additional days for late births, add days for premature births.

Cycle length affects when ovulation occurs. In a 28-day cycle, ovulation is around day 14. In a 35-day cycle, ovulation is around day 21, which means conception occurred about a week later than the 28-day estimate. Entering your actual cycle length makes the conception date more accurate.

The estimate is accurate to within about 5 to 7 days for the due date method and 3 to 5 days for the LMP method (if cycle length is known). The birth date method is least precise because delivery can occur 2 weeks before or after the due date. For medical purposes, ultrasound dating in the first trimester is the gold standard.

Not necessarily. Sperm can survive in the reproductive tract for 3 to 5 days, so conception (fertilization of the egg) may occur days after intercourse. The egg is viable for only 12 to 24 hours after ovulation. The conception date refers to when fertilization occurred, which could be up to 5 days after the last intercourse.

Yes, embedding the Retroactive Pregnancy Calculator is free. Hit the "Embed" button on this page, adjust the width, height, and theme, then grab the iframe code. It works on WordPress, Wix, Squarespace, Shopify, and plain HTML pages. No registration needed. Full instructions at calculory.com/services/embed-calculators.