Free Pregnancy Due Date Calculator Online
This free due date calculator estimates your baby's arrival date from your last menstrual period or conception date, and shows your current pregnancy week along with key milestones. Use it online, completely free.
Typical range: 21–45 days
Estimated Due Date
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How the Due Date Calculator Works
This free online due date calculator uses Naegele's rule, the standard clinical method for estimating delivery dates. The formula adds 280 days (40 weeks) to the first day of your last menstrual period (LMP). This works because pregnancy is counted from the LMP even though conception occurs approximately 2 weeks later.
If your cycle length differs from the standard 28 days, the due date calculator adjusts the estimate. A 32-day cycle means ovulation occurred around day 18 rather than day 14, shifting the due date forward by 4 days. If your cycle is 24 days, the due date moves 4 days earlier. You can calculate online instantly for any cycle length.
The due date is best understood as the center of a delivery window — about 80% of babies arrive within two weeks of this estimate. Only 5% of babies are born on their exact due date. Use this free tool as a planning guide and confirm with your healthcare provider.
Pregnancy Trimesters at a Glance
| Stage | Weeks | Key Events |
|---|---|---|
| First Trimester | Weeks 1–12 | Organ formation, risk of miscarriage highest |
| Second Trimester | Weeks 13–27 | Anatomy scan (~Week 20), fetal movement begins |
| Third Trimester | Weeks 28–40 | Rapid growth, lung maturation, positioning |
| Full Term | Week 37+ | Baby considered full term; delivery window opens |
| Due Date | Week 40 | Estimated delivery — only 5% deliver on exact date |
Key Pregnancy Milestones
Week 8
Heartbeat visible
Cardiac activity detectable on ultrasound; embryo is roughly 1.6 cm.
Week 12
End of first trimester
Miscarriage risk drops significantly. Most couples share the news after this milestone.
Week 20
Anatomy scan
Detailed ultrasound examines organs, spine, and limbs. Gender often determined here.
Week 24
Viability threshold
Babies born at 24+ weeks have a survival chance with intensive neonatal care.
Week 28
Third trimester begins
Rapid weight gain. Baby can open eyes and practice breathing movements.
Week 37
Full term
Baby considered fully developed. Birth at this stage no longer classified as preterm.
Tips After Getting Your Due Date
Schedule your first prenatal appointment as soon as possible — ideally before week 10.
An early ultrasound (before Week 14) is more accurate than LMP for due date confirmation.
Your due date may be revised at your first ultrasound scan — this is completely normal.
Start prenatal vitamins with folic acid immediately, even before your first appointment.
Bookmark this free online due date calculator to recheck your timeline as your pregnancy progresses.
Frequently Asked Questions
Disclaimer: This free online due date calculator provides an estimated delivery date for informational purposes only and is not a substitute for professional prenatal care. Due dates are estimates — individual pregnancies vary. Consult your qualified healthcare provider (OB-GYN, midwife, or family physician) for personalized medical advice, confirmation of your due date via ultrasound, and ongoing prenatal monitoring. This free tool does not replace professional obstetric care.
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