Pregnancy Conception Calculator

Understanding the Conception Window

Conception occurs when a sperm fertilizes an egg. This typically takes place within 24 hours of ovulation. Since sperm can live inside the female reproductive tract for up to 5 days, intercourse that occurs up to 5 days before ovulation can result in pregnancy.

Estimating Conception Dates

There are three common ways to estimate the conception date:

• Last Menstrual Period (LMP): If you have a regular 28-day cycle, conception typically occurs 14 days after the first day of your last period. For other cycle lengths, ovulation and conception happen approximately 14 days before the next expected period. Formula: $\text{Conception} = \text{LMP} + (\text{Cycle Length} - 14)\text{ days}$.
• Due Date: A standard pregnancy lasts 266 days (38 weeks) from conception. If your due date is known, the conception date is estimated by subtracting 266 days. Formula: $\text{Conception} = \text{Due Date} - 266\text{ days}$.
• Ultrasound Scan: If an early ultrasound estimates the baby's gestational age (which includes the standard 2 weeks before conception), the conception date is: $\text{Conception} = \text{Scan Date} - \text{Gestational Age} + 14\text{ days}$.