Free Due Date Calculator — When Is My Baby Due?

Frequently Asked Questions

How accurate is the due date calculator?

The calculator uses Naegele's rule, which is the standard method used by healthcare providers. It estimates your due date as 280 days (40 weeks) from the first day of your last menstrual period. Only about 5% of babies are born on their exact due date.

Can I use my conception date instead?

Yes! If you know your exact conception date, select 'Conception Date' mode. The calculator will add 266 days (38 weeks) to estimate your due date, as this is the average gestation from conception to birth.

When can I find out my baby's gender?

Gender can typically be determined by ultrasound around 16-20 weeks. However, using our expert Ramzi, Nub, or Skull theory analysis, you can get a prediction as early as 6-14 weeks from your ultrasound images.

How Does the Due Date Calculator Work?

Our free due date calculator uses Naegele's rule, the same method used by obstetricians and midwives worldwide. If you enter the first day of your last menstrual period (LMP), the calculator adds 280 days (40 weeks) to estimate your due date. If you know your conception date, it adds 266 days (38 weeks) instead.

Only about 5% of babies arrive on their exact due date, but it gives your healthcare team a reliable target window. Most births happen within two weeks before or after the estimated date.

Your Pregnancy Timeline by Trimester

First Trimester (Weeks 1-13)

Your baby develops all major organs. The heart begins beating around week 6. This is when early gender prediction using Ramzi theory becomes possible from your ultrasound.

Second Trimester (Weeks 14-27)

Your baby grows rapidly and begins moving. At 12-14 weeks, Nub theory analysis can predict gender from the nub angle visible on ultrasound.

Third Trimester (Weeks 28-40)

Your baby gains weight and matures. The 20-week anatomy scan often reveals gender. Skull theory analysis can also be performed from this point.

Due Date vs. Conception Date: Which Should I Use?

If you have regular periods, use your last menstrual period (LMP) — it's the standard medical method. If you tracked ovulation with OPKs or temping, use your conception date for a more precise estimate. IVF patients should use the transfer date (subtract 3 days for a 3-day transfer, or use the IUI date).

When Can You Predict Your Baby's Gender?

Knowing your due date helps you figure out exactly when gender prediction becomes possible. Here's a quick guide:

Week 6-10: Ramzi theory — placenta position analysis (accuracy ~60-70%)
Week 11-14: Nub theory — nub angle analysis (accuracy ~80-90% at 13 weeks)
Week 12+: Skull theory — cranial feature analysis (accuracy ~70-80%)
Week 16-20: Anatomy scan — traditional ultrasound gender determination

Ready to find out? Upload your ultrasound and our experts will analyze it using all three theories.

Due Date Calculator