Pregnancy Due Date Calculator

Estimated Due Date
–
based on Naegele's Rule

📅 Pregnancy Timeline

Current Gestational Age–
Estimated Conception Date–
End of 1st Trimester–
End of 2nd Trimester–
Full Term (40 weeks)–

What Is a Pregnancy Due Date Calculator?

This calculator estimates your due date and pregnancy timeline using Naegele's Rule, the standard method based on the first day of your last menstrual period (LMP) — the same approach commonly used by healthcare providers for an initial estimate.

How to Use the Pregnancy Calculator

  1. Enter the first day of your last menstrual period.
  2. Enter your average cycle length (28 days is typical, but adjust if yours differs).
  3. View your estimated due date and full pregnancy timeline.

Due Date Formula (Naegele's Rule)

Naegele's Rule
Due Date = LMP + 280 days (40 weeks), adjusted for cycle length

The standard calculation assumes a 28-day cycle with ovulation around day 14. If your cycle is longer or shorter, the calculator adjusts the estimate accordingly.

Worked Example

Example: LMP of January 1, 28-Day Cycle

Due date: January 1 + 280 days ≈ October 8

Estimated conception: around January 15 (day 14 of cycle)

This is an estimate — only about 5% of babies are born on their exact calculated due date.

Understanding Your Results

Due Date is a statistical estimate, not a precise prediction — most babies are born within about two weeks of this date. Gestational Age tracks how far along the pregnancy is, typically expressed in weeks. The trimester milestones give a general reference for pregnancy stages.

Important Notes

  • This calculator provides a general estimate; an ultrasound-based due date from a healthcare provider is typically more precise, especially for irregular cycles.
  • Full term is generally considered 39-40 weeks; babies born between 37-42 weeks are all within a typical range.
  • Always confirm pregnancy dating and monitor progress with a qualified healthcare provider.

Frequently Asked Questions

It's a widely used starting estimate, but actual delivery dates vary — only a small percentage of babies are born exactly on their calculated due date. An early ultrasound often provides a more precise estimate.

It's the standard formula for estimating a due date: adding 280 days (40 weeks) to the first day of the last menstrual period, assuming a typical 28-day cycle.

Gestational age is counted from the first day of the last menstrual period, while fetal (conceptional) age is counted from actual conception — gestational age is about two weeks ahead of fetal age.

This calculator adjusts for your specific average cycle length, since a longer or shorter cycle shifts the likely ovulation and conception date.

As early as possible in pregnancy — a first-trimester ultrasound is generally considered the most accurate method for dating a pregnancy.