Pregnancy Due Date Calculator

Estimate the due date from last menstrual period, conception date, or IVF transfer day, with gestational age and trimester milestones.

—Estimated due date
—Gestational age today
—Trimester

Milestones

—2nd trimester (14w0d)
—3rd trimester (28w0d)
—Full term (39w0d)

How this conversion works. Implements Naegele’s rule (LMP + 280 days, cycle-adjusted) and standard conception/IVF offsets per ACOG Committee Opinion 700 — Methods for Estimating the Due Date. Informational only — not medical advice. Confirm dating with your prenatal care provider; first-trimester ultrasound overrides calendar estimates.

How to use

  1. Pick the dating method — LMP, conception date, or IVF transfer.
  2. Enter the date (and cycle length for LMP).
  3. Read the estimated due date, gestational age today, and trimester milestones.

Frequently asked questions

How is the due date calculated from LMP?

Naegele’s rule: due date = first day of the last menstrual period + 280 days (40 weeks), adjusted by (cycle length − 28) days for longer or shorter cycles, per ACOG Committee Opinion 700.

How accurate is the estimated due date?

Only about 4–5% of babies arrive on the exact date; most are born within two weeks either side. First-trimester ultrasound is the most accurate dating method and takes precedence when it differs.

How does IVF dating work?

Embryo age is known precisely: due date = transfer date + 261 days for a day-5 blastocyst or + 263 days for a day-3 embryo.

When do trimesters change?

Using ACOG convention: second trimester begins at 14w0d, third at 28w0d, and full term runs 39w0d to 40w6d.

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