Conception Calculator
Estimate your conception date based on your last menstrual period, due date, or ultrasound information
Enter the first day of your last menstrual period
Enter Your Information
Fill in the form and click "Calculate Conception Date" to see your results
How Conception Dating Works
Conception typically occurs during ovulation, which for most women happens about 14 days after the first day of their last menstrual period. However, this can vary based on individual cycle length. Sperm can survive in the female reproductive tract for up to 5 days, so intercourse several days before ovulation can still result in pregnancy.
Why Use Last Menstrual Period?
Healthcare providers typically calculate pregnancy from the first day of your last menstrual period (LMP) rather than the actual conception date. This is because the LMP is usually more certain than the exact day of conception. This method assumes a 28-day cycle with ovulation on day 14, which is why pregnancy is calculated as 40 weeks (280 days) from the LMP.
Accuracy of Conception Calculators
Conception calculators provide estimates based on average cycles and typical ovulation patterns. The actual conception date may vary by several days. Early ultrasounds (performed in the first trimester) provide more accurate pregnancy dating and may adjust your due date. Your healthcare provider will use various methods including ultrasound measurements and physical examinations to determine the most accurate due date.