Pregnancy Due Date Calculator

Estimate your due date from your last period, conception date, IVF transfer, or an ultrasound reading.

What is LMP? LMP stands for "Last Menstrual Period" - the first day of your most recent period. Doctors use this as the standard starting point because the exact moment of ovulation or conception is rarely known.

What is Gestational Age? This is how far along your pregnancy is, counted in weeks and days from your LMP - not from conception. Because of this, a "40-week pregnancy" actually includes about 2 weeks before conception occurred, which is why it feels longer than 9 exact months.

Why 40 weeks? The 40-week standard (called "Naegele's Rule") is the globally accepted medical estimate. It starts from your LMP and accounts for the average ovulation window. Most healthy babies arrive between 38 and 42 weeks.

First Day of Last Period (the day your most recent period started)

Average Cycle Length (number of days from one period to the next - most people have 21 to 35 days)

Estimated Conception Date (the date you believe fertilization occurred)

The calculator adds 266 days (38 weeks) to your conception date to estimate your due date. This is because a full pregnancy is 40 weeks from LMP but only 38 weeks from the moment of conception.

IVF Embryo Transfer Date (the date the embryo was placed in the uterus)

Embryo Age at Transfer

3-Day Embryo (Cleavage Stage) 5-Day Embryo (Blastocyst)

The formula starts with 266 days from fertilization, then subtracts the embryo's age at transfer. For example, for a 5-day blastocyst: 266 - 5 = 261 days are added to the transfer date.

Date of Ultrasound (the date the scan was performed)

How many weeks and days pregnant were you measured at during that ultrasound?

Gestational Age - Weeks

Gestational Age - Days

This method works backward from your ultrasound reading to find your estimated LMP, then adds 280 days to get your due date. Early ultrasounds (6-12 weeks) tend to be the most accurate for dating.

Estimated Due Date (EDD)

Your Current Gestational Age

Pregnancy Milestones

This tool is for informational purposes only and is not a substitute for professional medical advice. Due dates are estimates - only about 5% of babies are born on their exact due date. Always confirm your due date with your healthcare provider.