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Pregnancy Due Date Calculator

Find out when your baby is due, how far along you are, and track all your important pregnancy milestones — from your first trimester through your due date.

Calculation Method

First Day of Last Period

Average Cycle Length (days)

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How to Use the Pregnancy Due Date Calculator

1
Select your calculation method. Most women use the Last Menstrual Period method — enter the first day of your last period and your average cycle length. If you know your conception date from ovulation tracking or IVF select the Conception Date method for a more precise estimate.
2
Your due date is calculated using Naegele Rule which adds 280 days (40 weeks) to your last menstrual period. If your cycle is longer or shorter than 28 days the calculator automatically adjusts your due date accordingly.
3
The results show your current gestational age, which trimester you are in, and a complete week-by-week milestone timeline from conception through your due date and beyond.
4
Download the free PDF to keep as a pregnancy reference or share with your partner, family, or healthcare provider at your first prenatal appointment.

Example Calculation

Scenario: LMP January 1, 2026 | Cycle Length 28 days

Due Date: October 8, 2026
Gestational Age (as of Mar 17): 10 weeks 5 days
Trimester: First Trimester
Full Term: September 17, 2026

Conception: January 15, 2026
Weeks Remaining: 29
Days Remaining: 205
Post-Term: October 22, 2026

Frequently Asked Questions

How is my due date calculated?

Your due date is calculated using Naegele Rule which adds 280 days or 40 weeks to the first day of your last menstrual period. This assumes a standard 28-day cycle with ovulation on day 14. If your cycle is longer or shorter the calculator adjusts accordingly. For example a woman with a 35-day cycle would have her due date shifted 7 days later than the standard calculation. Your doctor may also use ultrasound measurements in the first trimester to confirm or adjust your due date.

How accurate is the due date calculation?

The due date is an estimate — only about 5% of babies are born on their exact due date. Most babies arrive within 2 weeks before or after the calculated date. Due dates calculated from the last menstrual period are considered accurate within 5 to 7 days if your cycle is regular. First trimester ultrasound dating is the most accurate method and is typically accurate within 3 to 5 days. Your healthcare provider may adjust your due date based on ultrasound measurements at your first appointment.

What are the three trimesters of pregnancy?

Pregnancy is divided into three trimesters. The first trimester covers weeks 1 through 12 and includes the most critical period of fetal development. The second trimester covers weeks 13 through 26 and is often called the honeymoon trimester as many women feel their best during this period. The third trimester covers weeks 27 through 40 when the baby grows rapidly and prepares for birth. Full term is defined as 37 weeks and beyond.

What is gestational age vs fetal age?

Gestational age is counted from the first day of your last menstrual period and is the standard used by doctors. Fetal age or fertilization age counts from conception which typically occurs about 2 weeks after the LMP. This is why gestational age is always approximately 2 weeks more than fetal age. When your doctor says you are 10 weeks pregnant your baby has actually been developing for about 8 weeks since conception.

What does full term mean?

Full term means your baby is ready for birth without increased risk of complications. The American College of Obstetricians and Gynecologists defines full term as 39 to 40 weeks and 6 days. Early term is 37 to 38 weeks and 6 days — the baby is medically safe to deliver but may benefit from more time. Late term is 41 to 41 weeks and 6 days. Post term is 42 weeks or beyond at which point induction may be recommended due to increased risks.