Track your pregnancy journey with due date calculation, trimester milestones, weight monitoring, and baby development insights week by week.
Whether you’re confirming dates after conception, planning prenatal care, or preparing your birth plan, accurate timing matters. Our Pregnancy Calculator helps you estimate your due date using standard medical methods, shows trimester start and end dates, highlights typical developmental milestones by week, and outlines practical next steps for each stage. This guide explains how due dates are calculated, what a “due date” really means, how to interpret trimester and fetal-age differences, and how to combine this tool with the Ovulation Calculator, the Pregnancy Nutrition article, and our Age Calculator for a complete planning cluster.
A due date is an estimate — only ~4–5% of births happen on the exact estimated date. The EDD gives a planning window for care and logistics; your healthcare provider will adjust timing based on ultrasounds and clinical assessments.
The calculator supports the two most commonly used clinical approaches:
Early embryonic measurements have a small margin of error and provide a gestational age based on growth rather than recall. When ultrasound dating differs from LMP beyond a clinical threshold, providers typically use the ultrasound date.
The most common simple method is Naegele’s rule:
Practically, clinics typically add 280 days (40 weeks) to the LMP date (which is equivalent to Naegele’s rule) as a convenient shortcut. If you know the estimated conception date (for example based on ovulation tracking or assisted reproduction), adding roughly 266 days (38 weeks) gives a conception-based EDD. Our tool supports both inputs and clearly labels the basis for the estimate.
Gestational age is commonly reported by clinicians and counts from LMP; fetal age (or embryonic age) counts from conception and is about two weeks shorter than gestational age. When people say “I’m 12 weeks pregnant,” that usually means 12 weeks gestational (10 weeks fetal age if conception occurred 2 weeks after LMP). The calculator shows both values so you can understand appointment timing and trimester boundaries.
Trimester divisions are helpful for planning care and expectations. Typical breakdown:
Our calculator highlights these windows and counts down to recommended screening days, so you never miss timing-sensitive tests and scans.
If cycle length is irregular or LMP is uncertain, an early ultrasound (ideally in the first trimester) provides a reliable gestational age. The calculator accepts crown-rump length (CRL) or dated ultrasound gestational age if you have it, and updates the EDD accordingly while indicating the source of the date (LMP vs ultrasound).
Knowing typical milestones helps set realistic expectations:
The calculator provides countdowns to routine appointments so you can plan:
Use the output to create calendar reminders and to bring questions to each visit.
Routine pregnancies are typically managed in primary obstetric care, but contact a clinician promptly if you experience heavy bleeding, severe abdominal pain, decreased fetal movement (after fetal movement is expected), high fever, or any other acute concern. Consider referral to a maternal-fetal medicine specialist for known high-risk features (previous preterm birth, significant maternal medical conditions, multiple pregnancy, or abnormal screening results). Our tool includes guidance flags and suggests discussing specific results with your provider when values fall outside typical ranges.
Good prenatal nutrition and appropriate supplements support fetal development. Common practical recommendations (discuss with your clinician):
For pregnancies conceived via assisted reproductive technology (ART), dating conventions may differ — providers might prefer conception-based dating. Multiple pregnancies (twins, triplets) have different risk profiles and timing recommendations (e.g., recommended delivery timing may be earlier). The calculator supports conception-date input for IVF cycles and highlights when specialized care pathways commonly apply.
If labor does not start by the estimated due date (post-term), clinicians may discuss monitoring and induction options. “Due date” is a planning anchor; prenatal care adapts if pregnancy extends beyond the EDD. The calculator shows week-by-week risk/monitoring notes to help you and your provider discuss options.
If you export or print calculator results to share with your clinician, include both the input basis (LMP vs conception vs ultrasound) and the calculated EDD, gestational age, and the dates of suggested screening windows. Keep digital health logs secure and consider bringing printed copies to appointments if that helps.
For a complete planning experience, combine:
A due date is an estimate. Only about 4–5% of births occur on the exact EDD. Early ultrasound dating (first trimester) is reliably accurate to within about 5–7 days and often supersedes LMP when there's a discrepancy.
Use LMP if your cycles are regular and you remember the date. Use conception/ovulation date if you tracked ovulation precisely or conceived via ART. If there’s a conflict, early ultrasound is usually the tie-breaker.
Gestational age is calculated from LMP and is about two weeks longer than fetal (conception) age, which starts at fertilization. The calculator displays both so you can interpret clinical language accurately.
Irregular cycles reduce the reliability of LMP dating. An early ultrasound is typically recommended for accurate dating, and the calculator accepts ultrasound-based input for this reason.
Schedule your first prenatal visit when Pregnancy is confirmed—commonly 8–10 weeks gestation. Seek immediate care for heavy bleeding, severe pain, fever, or symptoms of pregnancy complications. For fertility concerns or repeated pregnancy loss, consult a specialist.
Use our Pregnancy Calculator to get an instant due date, track trimester milestones, and organize appointments and tests with confidence.
For more reading: Pregnancy Nutrition • Health & Weight Guide