Pregnancy Due Date Calculator

With a last menstrual period (LMP) it uses Naegele's rule: LMP plus 280 days, then adjusted by the difference between your cycle length and 28 days. A 32-day cycle adds 284 days instead of 280. With a conception date it adds 266 days (38 weeks) and counts gestational age from 14 days before conception, matching the standard LMP baseline.

Only about 5% of babies arrive on the exact due date, and roughly 90% are born within two weeks of it (about 37 to 42 weeks). First-trimester ultrasound dating is generally more precise than LMP, especially if your cycles are irregular. Treat this as a planning estimate, not a medical determination, and confirm the date with your provider.

By gestational age counted from the LMP, the first trimester runs weeks 1 to 12, the second covers weeks 13 to 26, and the third runs from week 27 through delivery. The calculator reports your current week and trimester from the same LMP baseline, so a conception date is shifted back 14 days first.

Schedule your first prenatal visit by 8 to 10 weeks from your LMP, or sooner if you already have an appointment. Seek care immediately for heavy bleeding, severe abdominal pain, sudden swelling, severe headaches, or reduced fetal movement after 28 weeks. This calculator is a planning tool only and does not replace professional medical advice.

Yes, when you use the LMP method. Naegele's rule assumes a 28-day cycle, so the calculator shifts the due date by one day for each day your cycle differs from 28: a 35-day cycle pushes it 7 days later, a 21-day cycle moves it 7 days earlier. It accepts cycle lengths from 20 to 45 days. Entering a conception date bypasses this adjustment entirely.