Due Date
Oct 10, 2026
Current Week
10w 0d
Days Remaining
210
Enter the first day of your last menstrual period
Typical range: 21-35 days (average: 28)
Your Due Date
Saturday, October 10, 2026
10
weeks + 0 days
210
days to go
End of first trimester
Week 12 • 3/28/2026
Anatomy scan (gender reveal)
Week 20 • 5/23/2026
Viability milestone
Week 24 • 6/20/2026
Third trimester begins
Week 28 • 7/18/2026
Full term
Week 37 • 9/19/2026
Due date
Week 40 • 10/10/2026
Inputs
Result
Due date = January 1 + 280 days + (28 - 28) = October 8, 2025. Conception = January 1 + 14 = January 15. Trimester 1 ends at week 12, trimester 2 at week 28.
Inputs
Result
Due date = March 15 + 280 + (30 - 28) = March 15 + 282 days = December 22, 2025. Conception = March 15 + 14 + 2 = March 31. The 2-day cycle adjustment shifts both due date and conception forward.
Due date is calculated using Naegele's Rule: Add 280 days (40 weeks) to the first day of your last menstrual period (LMP). This assumes a 28-day cycle with ovulation on day 14. For different cycle lengths, add or subtract the difference. Example: LMP January 1 → Due date October 8.
Pregnancy is counted from LMP (not conception) because most women know their last period date but not exact conception date. Conception typically occurs about 14 days after LMP, so "40 weeks pregnant" is actually 38 weeks since conception.
Only 4-5% of babies are born on their exact due date. About 80% are born within 2 weeks of the due date (38-42 weeks). First-trimester ultrasound (weeks 8-12) provides the most accurate dating, typically within ±5-7 days.
| Dating Method | Accuracy | When Used | Notes |
|---|---|---|---|
| LMP Calculation | ±2-3 weeks | Initial estimate | Assumes regular cycles |
| 1st Trimester Ultrasound | ±5-7 days | Weeks 8-12 | Most accurate |
| 2nd Trimester Ultrasound | ±10-14 days | Weeks 13-20 | Less accurate |
| 3rd Trimester Ultrasound | ±3 weeks | Weeks 28+ | Least accurate |
First trimester (weeks 1-12): Critical organ development, highest miscarriage risk. Second trimester (weeks 13-27): Rapid growth, movement felt, "honeymoon" phase. Third trimester (weeks 28-40): Baby gains weight, prepares for birth, most discomfort.
| Trimester | Weeks | Baby Development | Common Symptoms |
|---|---|---|---|
| First | 1-12 | All organs form, heartbeat | Nausea, fatigue, breast tenderness |
| Second | 13-27 | Movement, gender visible, growth | More energy, less nausea, showing |
| Third | 28-40 | Weight gain, brain development, viable | Back pain, frequent urination, Braxton Hicks |
Full term is 39 weeks 0 days to 40 weeks 6 days. Early term is 37-38 weeks, late term is 41 weeks, and post-term is 42+ weeks. Babies born at 39+ weeks have best outcomes for breathing, feeding, and brain development.
| Term | Gestational Age | Baby Readiness | Notes |
|---|---|---|---|
| Preterm | Before 37 weeks | May need NICU | Increased risks |
| Early Term | 37-38 weeks | Usually healthy | Slightly higher risks |
| Full Term | 39-40 weeks | Optimal | Best outcomes |
| Late Term | 41 weeks | Monitoring needed | May induce |
| Post-Term | 42+ weeks | Higher risks | Usually induce |
Key milestones: Week 6 - heartbeat detected. Week 10 - all organs formed. Week 12 - end of highest miscarriage risk. Week 18-22 - anatomy scan, feel movement. Week 24 - viability. Week 37 - considered early term. Week 39 - full term.
Call immediately for: heavy bleeding, severe abdominal pain, decreased fetal movement, severe headache with vision changes, contractions before 37 weeks, water breaking, fever over 100.4°F. Schedule first prenatal visit around weeks 8-10 after positive test.
When in doubt, call your healthcare provider. It's always better to check than to wait. Many concerns are false alarms, but some require immediate attention. Trust your instincts - you know your body best.
Read our guide
Read our guide
Read our guide
Calculate your body mass index
Find your daily calorie needs
Calculate total daily energy expenditure
Track your pregnancy and health metrics
Last Updated: Mar 11, 2026
This calculator is provided for informational and educational purposes only. Results are estimates and should not be considered professional financial, medical, legal, or other advice. Always consult a qualified professional before making important decisions. UseCalcPro is not responsible for any actions taken based on calculator results.