Calculate Your Due Date
📅 By LMP Date
🌱 By Conception Date
🩺 By Ultrasound
Estimated Due Date
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Week 1Trimester 1Week 13Trimester 2Week 27Trimester 3Week 40
⚠️ This tool provides estimates only. Always consult your doctor for accurate dating. Most accurate is an early ultrasound (6-12 weeks).
How Pregnancy Due Date Is Calculated
The standard pregnancy lasts 40 weeks (280 days) measured from the first day of your last menstrual period (LMP). This is called Naegele's rule:
- Due Date = LMP + 280 days (or LMP + 9 months + 7 days)
- Conception typically occurs ~14 days after LMP (mid-cycle ovulation)
- From conception, gestation is ~266 days
For irregular cycles, the calculation adjusts for actual cycle length. A 35-day cycle pushes ovulation (and conception) later, so add the extra days to your due date.
Three Trimesters of Pregnancy
- 1st Trimester: Week 1–13 (3 months) — major organ formation, morning sickness most common
- 2nd Trimester: Week 14–27 (months 4–6) — "honeymoon phase", baby movements felt around 18-22 weeks
- 3rd Trimester: Week 28–40 (months 7–9) — baby grows rapidly, more discomfort, preparation for birth
Week-by-Week Development Highlights
First Trimester (Weeks 1-13)
- Week 4-5: Baby's heart starts beating
- Week 6: Embryo is the size of a lentil
- Week 9: All major organs forming
- Week 12: Baby can suck thumb; first trimester screening tests
Second Trimester (Weeks 14-27)
- Week 16: Baby's sex can be seen on ultrasound
- Week 18-22: Anomaly scan (detailed ultrasound)
- Week 20: Halfway point! Baby kicks felt by mom
- Week 24: Baby reaches "viability" (could survive outside womb with NICU care)
Third Trimester (Weeks 28-40)
- Week 28: Baby weighs ~1 kg, can open eyes
- Week 32: Most growth in size now
- Week 37: Considered "early term" — baby can be born safely
- Week 39-40: Full term; labor can start any time
- Week 41+: Post-term; doctors may induce labor
Indian Pregnancy Care Schedule
Typical antenatal checkup schedule (varies by doctor):
- Weeks 0-28: monthly visits
- Weeks 28-36: every 2 weeks
- Weeks 36+: weekly until birth
Major scans
- Dating scan — 6-12 weeks (most accurate due date)
- NT scan — 11-13 weeks (Down syndrome risk)
- Anomaly scan — 18-22 weeks (detailed anatomy)
- Growth scans — 28, 32, 36 weeks (size and position)
Frequently Asked Questions
How is the due date calculated?
Most pregnancies last 280 days (40 weeks) from the first day of your last menstrual period (LMP). The calculator adds 280 days to LMP, or 266 days to conception date, or uses ultrasound dating for higher accuracy.
How accurate is the due date?
Only about 4% of babies arrive exactly on their due date. Most arrive within 2 weeks before or 1 week after. An early ultrasound dating scan (6-12 weeks) is the most accurate method — often more accurate than LMP-based calculation.
What if my cycles aren't 28 days?
The calculator adjusts for cycle length. For longer cycles (32 days), add 4 days to standard due date. For shorter (25 days), subtract 3. Most accurate is to use the conception date or early ultrasound.
Can I conceive when not ovulating?
No. Conception happens only when egg meets sperm during the fertile window (~5 days before ovulation + ovulation day). Tracking ovulation helps with conception or contraception planning.
What's the difference between weeks and months in pregnancy?
Doctors count in weeks (40 weeks total). Months are loose: 9 months in pregnancy = 36 weeks. The extra 4 weeks come from rounding lunar to calendar months. Most apps use "weeks" as the primary unit.
Should I rely on this calculator for medical decisions?
No. This is an estimate for planning. Always consult an obstetrician or gynecologist. Early ultrasound (6-12 weeks) gives the most accurate dating, and your doctor will use that as the official due date.
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