Pregnancy Due Date
Knowing your estimated due date (EDD) is the foundation of prenatal care — it determines your gestational week, prenatal screening timing, and when you'll likely meet your baby. Our calculator uses Naegele's rule (the standard method) from your last menstrual period, or works backwards from a known conception date or ultrasound gestational age.
Estimated Due Date
About the Pregnancy Due Date Calculator
Knowing your estimated due date (EDD) is the foundation of prenatal care — it determines your gestational week, prenatal screening timing, and when you'll likely meet your baby. Our calculator uses Naegele's rule (the standard method) from your last menstrual period, or works backwards from a known conception date or ultrasound gestational age.
How to use it
- Enter the first day of your last menstrual period (LMP).
- Or enter a known conception date (subtract ~14 days from the LMP equivalent).
- See your estimated due date, current gestational week, and trimester.
- View key milestone dates: 12-week NT scan, 20-week anatomy scan, 37-week full term.
Formula & methodology
Naegele's Rule: EDD = LMP + 9 months + 7 days (= LMP + 280 days). For irregular cycles, adjust: EDD = LMP + 280 days + (cycle length − 28). Conception-based: EDD = Conception date + 266 days (38 weeks). Gestational age = current date − LMP (in weeks + days).
Common use cases
- First prenatal appointment: confirming gestational age
- Planning maternity/paternity leave around expected delivery
- Scheduling trimester-specific screenings (NT scan, anatomy scan, glucose test)
- Understanding post-dates pregnancy if past 40 weeks
- IVF embryo transfer: calculating EDD from transfer date
Frequently asked questions
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