Due Date Calculator

This Due Date Calculator estimates your pregnancy due date, current gestational age, and trimester based on the first day of your last menstrual period (LMP).

Due date is calculated assuming a 28-day cycle (Naegele’s Rule).

Estimated Pregnancy Details

Estimated Due Date
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Gestational Age
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Current Trimester
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How a Pregnancy Due Date Is Calculated

A pregnancy due date is usually calculated using Naegele’s Rule, which assumes ovulation occurs about two weeks after the first day of the last menstrual period.

Due Date = LMP + 280 days (40 weeks)

What Is Gestational Age?

Gestational age is the length of the pregnancy measured from the first day of the last menstrual period. It is expressed in weeks and days and is used by healthcare providers worldwide.

Pregnancy Trimesters Explained

  • First Trimester: Weeks 1–12 (early development)
  • Second Trimester: Weeks 13–26 (rapid growth)
  • Third Trimester: Weeks 27–40 (final development)

Important Pregnancy Milestones

  • Heartbeat detectable around 6–7 weeks
  • First fetal movements felt around 16–20 weeks
  • Full-term pregnancy begins at 37 weeks

Only about 5% of babies are born on their exact due date. Most births occur within two weeks before or after the estimated date.

Frequently Asked Questions

Due date calculators provide estimates. Ultrasound measurements and medical evaluations offer more precise dating.
If your cycle is longer or shorter than average, ovulation timing may differ, slightly affecting the estimated due date.
No. The due date is an estimate. Most babies are born between 38 and 42 weeks of pregnancy.
A pregnancy is considered full term between 39 and 40 weeks.