Pregnancy Conception Calculator

Calculate when you likely conceived your baby

First day of your last menstrual period:

Your average menstrual cycle length (days):

Date of your ultrasound:

Gestational age determined by ultrasound (weeks):

Your Pregnancy Timeline

Conception Date (Estimated):

Due Date (Estimated):

Last Menstrual Period:

Current Gestational Age:

Pregnancy Timeline

Important Note

This calculator provides an estimate based on average pregnancy duration and ovulation timing. The actual conception date may vary by a few days. For the most accurate information, please consult with your healthcare provider.

How to Use the Pregnancy Conception Calculator

Our pregnancy conception calculator helps you estimate when you likely conceived your baby based on your last menstrual period (LMP), due date, or ultrasound information. Simply enter the requested information and our calculator will do the rest!

Understanding Your Results

The conception date is typically about 14 days after the first day of your last menstrual period for women with regular 28-day cycles. However, this can vary based on your unique cycle length and ovulation timing.

Calculation Methods

Last Menstrual Period (LMP): Estimates conception based on the start of your last period and your average cycle length.
Due Date: Works backward from your estimated due date to determine when conception likely occurred.
Ultrasound: Uses the gestational age determined by ultrasound to calculate the conception date.

Key Pregnancy Dates

Conception: When sperm fertilizes the egg (typically occurs 11-21 days after the first day of your last period).
Embryo Implantation: Usually occurs 6-12 days after conception.
First Trimester: Weeks 1-12 of pregnancy
Second Trimester: Weeks 13-27 of pregnancy
Third Trimester: Weeks 28-40 (or delivery) of pregnancy

Factors That Affect Conception Timing

Several factors can influence when conception occurs:

Cycle Length: Women with longer or shorter cycles may ovulate earlier or later than the average day 14.
Sperm Lifespan: Sperm can live up to 5 days in a woman's reproductive tract.

Egg Viability: Once released, an egg can be fertilized for about 12-24 hours.
Irregular Cycles: Make conception timing harder to predict.

Common Questions About Conception

It's difficult to determine the exact day of conception with complete certainty unless you underwent a procedure like IVF. Natural conception can typically occur within a window of several days around ovulation. Our calculator provides an estimate based on typical pregnancy patterns.

Healthcare providers start counting pregnancy weeks from the first day of your last menstrual period (LMP) because it's a more reliable date to remember than when conception occurred. This means that at the time of conception, you're actually considered to be about 2 weeks pregnant in medical terms, even though fertilization just happened.

This calculator provides an estimate based on average pregnancy duration (40 weeks from LMP) and typical ovulation timing. However, individual variations in cycle length, ovulation timing, and the exact moment of fertilization can affect the actual conception date. For the most accurate dating of your pregnancy, consult with your healthcare provider who may use ultrasound measurements for more precise dating.

If you have irregular periods, the calculations based on last menstrual period may be less accurate. In this case, using the due date provided by your healthcare provider (often based on ultrasound measurements) or ultrasound dating will likely give you a more accurate conception estimate.