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🤰 Pregnancy Due Date Calculator

Calculate your estimated due date and find out how many weeks pregnant you are. Based on the first day of your last menstrual period. Instant and accurate!

✏️ Enter Your Values
💜 This calculator gives an estimated due date. Your doctor will confirm the exact date through clinical assessment and ultrasound.
✨ Your Result
Result
🦉Owl's Explanation
🤰
Fill in the values on the left
and click Calculate! ✨

🤔 How Does This Tool Work?

The Pregnancy Due Date Calculator uses Naegele's Rule — the standard medical formula used by doctors worldwide:

Due Date = First day of last period + 280 days + (cycle length − 28) days

For a standard 28-day cycle: just add 280 days (40 weeks) to the first day of your last period.

If your cycle is longer or shorter than 28 days, we add or subtract the difference. For example, a 30-day cycle: 280 + (30−28) = 282 days total.

We also calculate your current gestational age in weeks by finding the difference between the first day of your last period and today's date.

Remember: This is an estimate. Your doctor will confirm with clinical assessment and ultrasound scanning.

❓ FAQ
How is the due date calculated?▼
The standard method (Naegele's Rule) adds 280 days (40 weeks) to the first day of your last menstrual period. If your cycle is longer or shorter than 28 days, we adjust accordingly. This gives your estimated due date.
How accurate is the due date calculator?▼
The estimated due date is accurate to within 2 weeks in either direction for most pregnancies. Only about 5% of babies are actually born on their exact due date. Your doctor will confirm with an ultrasound scan.
What is the difference between gestational age and fetal age?▼
Gestational age is counted from the first day of your last period (the standard medical measurement). Fetal age (actual age of the baby) is about 2 weeks less than gestational age, since conception usually occurs around day 14 of the cycle.
What if I have an irregular cycle?▼
Enter your average cycle length if you know it. If your cycles vary greatly, the calculator may be less accurate. An early ultrasound scan (between 8 and 14 weeks) is the most accurate way to determine your due date.
When should I see a doctor?▼
As soon as you get a positive pregnancy test! Early prenatal care is very important for both mother and baby's health. Your doctor will confirm the due date, check your health, and advise on vitamins and lifestyle during pregnancy.
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