Your pregnancy journey
Pregnancy Calculator
Find your due date, current week, trimester, and week-by-week milestones — in seconds.
Estimated Due Date
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Wk 1–13
Wk 14–26
Wk 27–40
Week-by-Week Milestones
How does the pregnancy calculator work?
Our calculator uses the Naegele’s Rule — the gold-standard obstetric formula — to estimate your expected due date (EDD). It adds 280 days (40 weeks) to the first day of your last menstrual period (LMP) and adjusts for your personal cycle length.
For IVF pregnancies, the age of the embryo at transfer is factored in (Day 3 = 17 days subtracted from transfer date; Day 5 = 15 days; Day 6 = 14 days) to give you the equivalent LMP date.
“`Frequently Asked Questions
How accurate is a due date calculator?
Due date calculators are accurate to within 1–2 weeks for most pregnancies. Only about 4% of babies are born exactly on their due date, with most arriving between 38–42 weeks. An ultrasound in the first trimester provides the most precise dating.
What is a trimester?
Pregnancy is divided into three trimesters. The first trimester covers weeks 1–13 (organ formation). The second trimester spans weeks 14–26 (rapid growth, movement). The third trimester runs from week 27 to birth (lung maturation, weight gain).
What if I don’t know my LMP?
Use the “Conception” tab if you have a reasonably accurate conception date. Alternatively, switch to the “Due Date” tab if your doctor has already given you an estimated due date from an ultrasound scan.
What does LMP mean?
LMP stands for Last Menstrual Period — specifically the first day of your most recent period before becoming pregnant. It is the universal clinical starting point for calculating gestational age.
How is IVF due date calculated differently?
For IVF pregnancies, embryo age at transfer is known precisely. A Day-5 blastocyst is already 5 days old at transfer, so the equivalent LMP is 19 days before the transfer date (14 days typical luteal + 5 days embryo age). Our calculator handles this automatically.
What are the key development milestones?
Key milestones include the heartbeat starting around week 6, all major organs forming by week 10, the anatomy scan at week 20, viability threshold around week 24, and lung maturation after week 34. Our milestone timeline shows these relative to where you are today.