Calculator tool
Conception is estimated about 266 days before the due date, or around ovulation for LMP-based dating. The possible window spans several days because ovulation and sperm survival vary.
Review the inputs carefully and treat the output as an estimate. For decisions involving money, taxes, health, law, or security, compare the result with trusted professional guidance when needed.
Can I know the exact conception date?
Usually no. Conception date is an estimate because ovulation timing varies and sperm can survive for several days.
Why does ultrasound help?
Early ultrasound can provide a clinical gestational-age estimate, which can be used to work backward to a likely conception window.
Ovulation Calculator
Estimate your ovulation date and 6-day fertile window based on your last period and average cycle length.
Open toolDue Date Calculator
Calculate an estimated due date from LMP, conception date, ultrasound gestational age, or IVF embryo transfer.
Open toolPregnancy Calculator
Estimate current pregnancy week, due date, trimester, and milestone dates from LMP, due date, conception, ultrasound, or IVF transfer.
Open tool