Due Date Calculator
Due Date Calculator
Calculating your due date helps you plan for pregnancy milestones and prepare for your baby's arrival. This calculator uses Naegele's Rule, the standard method used by healthcare providers.
Key Terms
- LMP (Last Menstrual Period) — The first day of your last period.
- Due Date — Estimated delivery date, calculated as 40 weeks from LMP.
- Gestational Age — How far along the pregnancy is, measured from LMP.
- Fertilization Age — Actual age of the fetus, typically 2 weeks less than gestational age.
- Trimester — Pregnancy is divided into three 13-week periods.
Naegele's Rule
Due Date = LMP + 1 Year - 3 Months + 7 Days
Or simply: LMP + 280 days (40 weeks)
Pregnancy Milestones
- Week 4-6 — Heart begins to beat
- Week 8 — All major organs forming
- Week 12 — End of first trimester, miscarriage risk drops
- Week 20 — Anatomy scan, halfway point
- Week 24 — Viability threshold
- Week 28 — Third trimester begins
- Week 37-42 — Full term
Tips for Expectant Parents
- Start prenatal vitamins with folic acid before conception if possible.
- Schedule your first prenatal visit around 8 weeks.
- Only about 5% of babies are born on their exact due date.
- Due dates are estimates — normal delivery can occur 2 weeks before or after.
- Track fetal movement starting around 20 weeks.