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Pregnancy Due Date Calculator

Calculate your estimated due date, current pregnancy week, and trimester.

Select a method and enter a date to calculate your due date.

How is a Pregnancy Due Date Calculated?

The most commonly used method for calculating an estimated due date (EDD) is Naegele's Rule, developed by German obstetrician Franz Naegele in the early 19th century. It adds 280 days (40 weeks) to the first day of your last menstrual period (LMP). This works because pregnancy is counted from the LMP, not conception — meaning you are technically "2 weeks pregnant" at the time of conception. The 280-day average is based on a 28-day menstrual cycle.

If you know your conception date, the calculator adds 266 days (280 − 14). For IVF pregnancies, the calculation adjusts based on the embryo transfer date: a 3-day transfer adds 263 days, while a 5-day blastocyst transfer adds 261 days. All methods give an estimate — only about 5% of babies are born exactly on their due date, but 80% are born within 2 weeks of it.

How to Use the Pregnancy Calculator

  1. Choose your Calculation Method: Last Period (most common), Conception Date, or IVF Transfer.
  2. Enter the relevant date.
  3. For IVF, also select whether it was a 3-day or 5-day (blastocyst) transfer.
  4. Your estimated due date, current pregnancy week, trimester, and days remaining are shown instantly.
  5. Scroll down to see key milestone dates throughout your pregnancy.

Why Use Our Pregnancy Calculator?

  • Three Input Methods — LMP, conception date, and IVF (3-day or 5-day transfer).
  • Milestone Timeline — Key dates from 8 weeks to 40 weeks shown automatically.
  • Progress Bar — Visual display of how far along you are.
  • Trimester Identification — Know which trimester you are in at a glance.
  • Completely Private — No data stored; calculations run locally in your browser.

Frequently Asked Questions

The standard method is Naegele's Rule: take the first day of your last menstrual period (LMP), add 1 year, subtract 3 months, and add 7 days. Equivalently, add 280 days to the LMP. This gives you the Estimated Due Date (EDD). Your doctor may adjust this based on ultrasound measurements, especially in the first trimester when measurements are most accurate for dating.

Naegele's Rule is a standard method for calculating EDD, named after Franz Karl Naegele (1778–1851). It assumes a regular 28-day cycle and ovulation on day 14. The formula is: EDD = LMP + 280 days. It is widely used because it is simple and reasonably accurate for women with regular cycles. Women with cycles significantly shorter or longer than 28 days may have less accurate estimates from this method.

The EDD is an estimate, not a precise prediction. Only about 4–5% of babies are born exactly on their due date. Approximately 80% of babies are born within 2 weeks either side of the EDD. First-trimester ultrasounds are more accurate for dating (±5–7 days) than LMP-based calculations. Your doctor will establish an official EDD, often combining LMP dating with ultrasound findings.

Pregnancy is divided into three trimesters: the First Trimester covers weeks 1–12 (organ formation, highest miscarriage risk, morning sickness common); the Second Trimester covers weeks 13–27 (often the most comfortable, fetal movements begin, anatomy scan around 20 weeks); the Third Trimester covers weeks 28–40+ (rapid growth, preparation for birth, 37 weeks is considered full term). Birth before 37 weeks is preterm.

Quick Facts

  • ✓ Supports LMP, conception date, and IVF
  • ✓ Calculates week, trimester, days remaining
  • ✓ Shows key pregnancy milestone dates
  • ✓ Visual pregnancy progress bar
  • ✓ All calculations run privately in browser

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