Due Date Calculator

A due date calculator helps you estimate when your baby is likely to arrive. Whether you want to count from your last period, your conception date, or work backwards from a known due date, this tool gives you a clear answer without the mental math.

For many moms, knowing their due date and current week of pregnancy makes it easier to plan doctor visits, prepare for the baby, and feel more in control during pregnancy. It can also help you track important milestones as your pregnancy progresses.

How Due Dates Are Usually Calculated

Most due date calculators use a method called Naegele's Rule. This method adds 280 days (40 weeks) to the first day of your last menstrual period. It assumes a regular 28-day cycle. If your cycle is longer or shorter, the estimated due date will adjust accordingly.

If you know your exact conception date, the calculator adds 266 days from that date to estimate your due date.

Why Your Due Date Might Change

Your estimated due date is just that, an estimate. Early ultrasounds (usually done between 8 and 14 weeks) are often more accurate than calculations based on your last period. Your doctor may adjust your due date if the ultrasound measurements are significantly different from your original calculation. This is very common and nothing to worry about.

What to Expect as Your Due Date Approaches

As you get closer to your due date, your body will start showing signs that labor may be near. These can include Braxton Hicks contractions, losing your mucus plug, or your baby dropping lower into your pelvis. Every pregnancy is different, so try not to compare your experience with others. If you have any concerns, always reach out to your healthcare provider.

How to Use This Calculator

1. Enter the first day of your last menstrual period using the date picker.
2. Select your average cycle length (between 21 and 35 days).
3. Choose your preferred calculation method: Last Period, Conception Date, or Reverse Due Date.
4. Click "Calculate" to see your estimated due date, current week of pregnancy, trimester, and days remaining.

How This Calculator Works

This calculator uses the standard medical method for estimating due dates. It adds 280 days to the first day of your last period, or 266 days from your conception date. If you choose the Reverse Due Date option, it works backwards from your known due date to show your estimated conception date and current progress.

Worked Example

If your last period started on June 1, 2026 and your cycle is 28 days long:

• Estimated due date: March 8, 2027
• Current week (as of June 16, 2026): 2 weeks pregnant
• Trimester: First trimester
• Days remaining until due date: Around 265 days

If your conception date was June 15, 2026, the estimated due date would also be March 8, 2027.

Frequently Asked Questions

How accurate is a due date calculator?
Due dates are estimates, not exact predictions. Only about 4% of babies are born on their exact due date. Most babies arrive between 37 and 42 weeks. Your healthcare provider may adjust your due date based on ultrasound results.

Why does my due date sometimes change?
Early ultrasounds are often more accurate than calculations based on your last period. If the measurements from your ultrasound are different from your original due date, your doctor may update it. This is normal and happens to many women.

What's the difference between using my last period and my conception date?
The last period method estimates your due date from the first day of your last menstrual period. The conception date method uses the actual day fertilization happened. If you know your conception date, that method is usually more accurate.

Can I use this calculator if I have irregular periods?
Yes, you can still use it by adjusting your cycle length. However, if your cycles are very irregular, the estimate may be less accurate. In that case, an early ultrasound is usually the most reliable way to date your pregnancy.

Is it normal to feel anxious about my due date?
Yes, it's very common to feel nervous or impatient as your due date gets closer. Try to remember that your baby will come when they are ready. Focus on taking care of yourself and reaching out for support when you need it.