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Your estimated due date (EDD) is one of the most meaningful numbers in a pregnancy. It anchors every prenatal appointment, screening test, and preparation plan for the next nine months. But only about 5% of babies arrive on their exact due date. The EDD is a statistical midpoint: the 40-week mark (280 days) from the first day of your last menstrual period, based on an average cycle length of 28 days.
If your cycles are longer or shorter, your EDD shifts accordingly — this calculator adjusts automatically using the cycle length you enter. A 32-day cycle, for example, shifts the EDD four days later than the standard 28-day calculation. IVF patients get an even more precise calculation because the embryo's exact developmental age at transfer is known: a Day 3 embryo is 3 days old, so 263 days are added to the transfer date; a Day 5 blastocyst is 5 days old, so 261 days are added.
Whether your EDD shifts slightly after an early ultrasound or stays consistent throughout, it serves as your calendar anchor — for scheduling the nuchal translucency scan (weeks 11–14), the anatomy scan (weeks 18–22), the glucose screening (weeks 24–28), and the Group B strep test (weeks 35–37). Each of these has a specific window that matters clinically.
Gestational age is counted from the first day of your last menstrual period — not from conception. That means in week 1 and week 2, you are not yet technically pregnant. Conception typically happens around day 14 of a 28-day cycle — the end of week 2. By week 4, the newly implanted embryo is producing hCG and most home pregnancy tests can detect it. By week 8, all major organ systems have begun forming and the embryo is officially a fetus.
Week 12 marks the end of the period of highest miscarriage risk, and many people choose this point to share their news. Week 20 is the halfway point and typically when the detailed anatomy scan is performed. Week 24 is the viability milestone — babies born this early have a chance of survival with intensive NICU care. Week 37 is "early full-term" — medically acceptable for delivery. Only 5% of babies are born exactly on their due date; around 80% are born within two weeks either side.
The fruit and vegetable size comparisons in this tool are a popular visual aid based on WHO fetal growth standards. Seeing that your baby went from a blueberry at week 7, to a lime at week 12, to a banana at week 20, to a cantaloupe at week 34 gives a concrete sense of the extraordinary pace of fetal growth. Actual measurements vary between pregnancies — these are midpoint estimates for a typical singleton pregnancy.
Once you know your estimated due date, the rest of the prenatal calendar falls into place. Most providers see you monthly until 28 weeks, every two weeks from 28 to 36 weeks, and weekly from 36 weeks until delivery — roughly 12 to 15 visits in all. Layered on top are the time-sensitive screenings: the nuchal translucency scan at 11–13 weeks, the anatomy scan at 18–22 weeks, glucose screening for gestational diabetes at 24–28 weeks, and the Group B Strep swab at 36–37 weeks. This calculator turns those week numbers into real calendar dates for your pregnancy, so you can see at a glance when each window opens.
With Due Date Pro you can export the whole schedule to your phone's calendar as an .ics file, download it as a spreadsheet, or print a clean one-page timeline to bring to your OB or midwife. Pro also includes an on-device kick counter for tracking your baby's movements in the third trimester and a contraction timer for early labor — both store their history privately on your device, with nothing sent to a server. The week-by-week explorer, dated milestone timeline, and due-date calculation itself remain completely free.