Estimate when conception occurred using your due date, last period date, or ultrasound information. Get a conception window range.
Conception date estimates are approximations with a ±2 day window. The exact moment of conception cannot be determined without advanced medical procedures. Factors like sperm survival (up to 5 days) and ovulation timing add uncertainty.
Gestational age is counted from the last menstrual period (LMP), which is about 2 weeks before conception. Fetal age (conceptional age) starts from actual conception. So at conception, gestational age is approximately 2 weeks.
Early ultrasound (6–9 weeks) provides the most accurate dating, with ±3–5 day accuracy. Due date calculations are next best. LMP-based estimates assume a regular 28-day cycle, which varies between individuals.