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Gestational Age from Due Date

Gestational age on a given date equals 280 days minus the days remaining until the estimated due date (EDD), expressed in completed weeks and days. Term is 37w0d–41w6d.

  • Estimated due date (EDD)
  • Date to calculate GA on
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Interpretation

ResultMeaning
< 14w0dFirst trimester
14w0d–27w6dSecond trimester
≥ 28w0dThird trimester
34w0d–36w6dLate preterm
37w0d–41w6dTerm
≥ 42w0dPost-term

Formula

GA (days) = 280 − (EDD − date) · weeks = ⌊GA ÷ 7⌋, days = GA mod 7

Clinical pearls

  • GA is counted from the LMP, so it is about 2 weeks more than the embryo's actual age.
  • Use the best obstetric EDD (LMP confirmed or revised by early ultrasound).

Examples

ga on 2026-06-01 if edd 2026-10-08how many weeks pregnant, due date Dec 1 2026, today Aug 15 2026gestational age edd 2027-01-10 as of 2026-10-14

FAQ

How many weeks pregnant am I if my due date is known?

Subtract the days remaining until the due date from 280, then divide by 7: the whole number is completed weeks and the remainder is days.

What gestational age is full term?

Term is 37w0d to 41w6d; 39w0d–40w6d is "full term" in the ACOG classification.

Evidence

  1. ACOG Committee Opinion No 700: Methods for Estimating the Due Date. Obstet Gynecol 2017;129:e150–4.

Pediatrics & Obstetrics · Reviewed 2026-10-14 · Methodology