Pregnancy Calculator
Track gestational age, current trimester, and key milestone dates through your pregnancy.
Estimated due date
February 20, 2027
What Your Result Means
Gestational age is measured in weeks from the first day of your last menstrual period (LMP), not from the actual date of conception - which is why "week 4" of pregnancy is only about 2 weeks after conception.
How It Is Calculated
Due date = LMP + 280 days (Naegele's rule)
Conception estimate = LMP + 14 days
Worked Example
If your last period started on January 1st, your estimated due date is October 8th, about 40 weeks later.
Important Assumptions
- Assumes a standard 28-day cycle with ovulation around day 14.
- Only about 5% of babies are born on their exact due date - this is an estimate, not a guarantee.
- Your healthcare provider may adjust your due date based on an ultrasound, which can be more accurate than LMP-based dating.
Frequently Asked Questions
- Why is pregnancy counted as 40 weeks if it's only 9 months?
- Because gestational age starts counting from your last period, not conception - adding about 2 extra weeks compared to counting from the actual conception date.
- Is this a substitute for a doctor's estimate?
- No. This gives a general estimate using standard dating rules. Your doctor's ultrasound-based due date, if available, is typically more precise and should be used for medical decisions.
Related Calculators
Methodology
This calculator uses Naegele's rule, the standard method for estimating a due date. See our methodology page for details.
This calculator provides estimates for educational purposes only. It does not provide medical diagnosis and is not a substitute for professional medical advice. Consult a qualified healthcare provider about your health.