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Free gestational age calculator from LMP to any reference date (including “today”). See completed weeks and days, trimester, and an LMP-based estimated due date (280 days / 40 weeks). Pair with our reverse due date and pregnancy tools.
Last updated: April 13, 2026
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Use today’s date for current gestational age, or an ultrasound / visit date for dating at that time.
Gestational age
27 weeks 5 days
194 completed days since LMP (27 w + 5 d)
Estimated due date (EDD)
2026-07-08
LMP + 40 weeks (280 days), Naegele-style
Versus EDD
86 days before EDD
Trimester 2
Second trimester (14 weeks 0 days through 27 weeks 6 days)
LMP dating vs ultrasound
Many pregnancies are dated by first-trimester ultrasound when LMP is unknown or inconsistent. This tool uses LMP only; use documented clinical EDD when it differs.
Enter the first day of the last period and any visit date to reproduce the “weeks pregnant” math used in many clinics before ultrasound adjustment.
Shows an estimated due date and how far the reference date is before or after that LMP-based EDD.
Maps completed weeks to the trimester bands used in most US teaching materials.
Full term is often cited as 37–40 weeks gestation for delivery timing discussions; EDD by LMP is 40 weeks (280 days) from the first day of LMP. Always follow your clinician’s documented due date when it differs.
The calculator finds the number of whole calendar days between the LMP date and your chosen reference date, then splits that into completed weeks and extra days. It adds 280 days to LMP for an estimated due date and compares the reference date to that EDD. Trimester follows completed weeks: under 14 for first, 14–27 for second, 28+ for third.
Gestational days = calendar days from LMP to reference dateWeeks = floor(gestational days ÷ 7); Days = remainderEDD = LMP + 280 daysAfter delivery, use the adjusted age calculator for premature infants.
Get a Custom Calculator for Your PlatformIf the reference date falls exactly 168 days after LMP, the calculator reports 24 weeks 0 days, typically third trimester begins later at 28 weeks—so this example sits in the second trimester.
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