Pregnancy Due Date Calculator

How Due Dates Are Calculated

We use Naegele's rule, the standard method: add 280 days (40 weeks) to the first day of your last menstrual period. This assumes a regular 28-day cycle with ovulation on day 14.

Healthcare providers use this method worldwide as a starting point. First trimester ultrasound (usually 8–14 weeks) often provides a more precise date if there's a discrepancy.

Pregnancy Trimesters

Trimester	Weeks	What's Happening
1st Trimester	1–12	Organ formation, morning sickness common
2nd Trimester	13–26	Rapid growth, you may feel movement
3rd Trimester	27–40	Final development, baby gains most weight

Setting Realistic Expectations

• Only about 5% of babies arrive on their exact due date
• Most births happen within 2 weeks before or after the due date
• A "full-term" pregnancy ranges from 37 to 42 weeks
• Your provider will track progress at prenatal visits

Confirm With Your Provider

This calculator gives an estimate. Your healthcare provider will confirm your due date using ultrasound and other factors. They can also create your prenatal care plan, which is the most important next step.