Pregnancy Due Date Calculator

Estimate your baby's due date based on your last menstrual period or conception date with weekly milestones.

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1. Choose your calculation method - last menstrual period (LMP) or known conception date. 2. Enter the date of your last period or the conception date. 3. View your estimated due date calculated using Naegele's Rule. 4. Check your current week of pregnancy and trimester. 5. Review developmental milestones and key dates for each trimester.

About This Tool

Finding out when your baby is expected to arrive is one of the most exciting moments of pregnancy. Our Pregnancy Due Date Calculator estimates your due date using either your last menstrual period (LMP) date or a known conception date, following the same method used by healthcare providers worldwide.

The calculator uses Naegele's Rule, which adds 280 days (40 weeks) to the first day of your last menstrual period. If you enter a conception date instead, it adds 266 days (38 weeks). Along with your due date, the calculator shows your current week of pregnancy, trimester, and key developmental milestones for each stage.

Keep in mind that only about 5% of babies arrive on their exact due date. Most births occur within two weeks before or after the estimated date. Your healthcare provider may adjust your due date based on ultrasound measurements, especially during the first trimester when dating is most accurate.

Formula / How It Works

Naegele's Rule: Due date = LMP + 280 days (40 weeks). From conception date: Due date = conception + 266 days (38 weeks). Assumes a 28-day menstrual cycle.

Frequently Asked Questions

The most common method is 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. If you know the conception date, add 266 days (38 weeks) instead.
Due date calculators provide an estimate. Only about 5% of babies are born on their exact due date. Most births occur within a two-week window around the estimated date. First-trimester ultrasound dating is typically accurate to within 5-7 days.
If your cycle is longer or shorter than 28 days, your ovulation and conception likely occurred on a different day than assumed. Adjust by adding or subtracting the difference from 28. For example, with a 32-day cycle, add 4 extra days to the LMP-based estimate.
The first trimester is weeks 1-12, when major organs form. The second trimester is weeks 13-26, when the baby grows rapidly and movements become noticeable. The third trimester is weeks 27-40, when the baby gains weight and prepares for birth.
Schedule your first prenatal visit between weeks 6 and 8 of pregnancy. Earlier visits may be recommended if you have a high-risk condition, a history of complications, or are unsure about your dates. Contact your healthcare provider as soon as you get a positive test.

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