Conception Date Calculator
Estimate when conception may have happened from your due date, or estimate your due date from a known conception date.
This page is for general pregnancy planning and date guidance only. It is not medical advice, diagnosis, or treatment. Pregnancy dates are estimates and can change after a scan or advice from your midwife, GP, or maternity team. Always speak to a qualified healthcare professional if you have symptoms, concerns, or questions about your pregnancy.
Conception date calculator
Estimate conception date from a due date, or estimate a due date from a known conception date.
How conception date is estimated
A due date is often estimated as 40 weeks from the first day of the last menstrual period. Conception usually happens around two weeks after that point, so this calculator uses 266 days between conception and estimated due date.
Why this is only an estimate
Ovulation timing, cycle length, implantation timing, and dating scan measurements can all affect pregnancy dating. If your midwife or scan gives you an official due date, use that date for care planning.