Conception Date Calculator
Instantly estimate your conception date and fertile window from your due date, last menstrual period, or your baby’s birth date. Free, easy-to-use pregnancy dating tool.
Estimate Your Conception Date
Choose what you know — your due date, last menstrual period, or your baby’s birth date — to get an instant estimate of the likely conception date and fertile window.
Pregnancy Details
Select your known date to estimate conception
Conception Estimate
Estimated conception date and fertile window
Pregnancy Timeline Milestones
Typical timing of key milestones measured from the first day of the last menstrual period (LMP).
| Milestone | Description | Approx. Timing |
|---|---|---|
| Last Menstrual Period (LMP) | Standard pregnancy dating reference point | Day 0 |
| Ovulation | Egg release; conception typically occurs here | ~Day 14 |
| Implantation | Fertilised egg implants in the uterus | ~Day 21–24 |
| First Missed Period | Common point pregnancy is first suspected | ~Day 28 |
| Full Term Due Date | Estimated delivery date (EDD) | Day 280 (40 weeks) |
Conception Date FAQ
Everything you need to know about estimating a conception date.
Conception typically occurs around ovulation, which is usually about 14 days before the start of the next menstrual period. From a known due date, conception is commonly estimated as 266 days before that date, since full-term pregnancy is roughly 38 weeks from conception.
The last menstrual period (LMP) is the date your last period started, and is the standard reference point doctors use to date a pregnancy. Conception, however, usually happens around two weeks after the LMP, near the time of ovulation.
Ovulation timing varies between individuals and cycles, and sperm can survive in the body for several days before fertilisation occurs. This means the actual date of conception can fall anywhere within a fertile window of several days, not on a single fixed date.
No. This calculator provides a statistical estimate based on typical pregnancy length and cycle timing. For medical or legal certainty, an early dating ultrasound performed by a healthcare provider is far more accurate.