Pregnancy Due Date Calculator
Estimate your due date and track key pregnancy milestones week by week.
Weeks 1–12
Weeks 13–26
Weeks 27–40
Key Milestones
Free Pregnancy Due Date Calculator
The Toolts Pregnancy Due Date Calculator estimates when your baby is expected to arrive based on either your last menstrual period (LMP) or your conception date. It also shows your current week of pregnancy, trimester, and important milestones throughout the 40-week journey. All calculations happen privately in your browser.
How Due Dates Are Calculated
The most common method is Naegele's rule, which adds 280 days (40 weeks) to the first day of your last menstrual period. This assumes a standard 28-day cycle with ovulation occurring on day 14. If your cycle is longer or shorter than 28 days, the calculator adjusts the due date accordingly, since ovulation typically occurs about 14 days before the start of the next period regardless of cycle length.
LMP vs Conception Date
If you know your conception date, the calculator adds 266 days (38 weeks), since conception typically occurs about 2 weeks after the start of the menstrual period. The LMP method is more commonly used because most women know when their last period started, even if they don't know the exact day of conception. Both methods produce the same estimated due date when the cycle length is properly accounted for.
How Accurate Are Due Dates?
Only about 4 to 5 percent of babies are born on their exact due date. Most babies arrive within two weeks before or after the estimated date. The due date is best understood as the middle of a window rather than a precise prediction. First-time mothers tend to deliver slightly later than the due date on average, while subsequent pregnancies may be closer to or slightly before the estimate. An ultrasound in the first trimester can provide a more accurate due date than calculation alone.
Understanding Trimesters
Pregnancy is divided into three trimesters, each lasting about 13 weeks. The first trimester (weeks 1 through 12) is when major organs and structures begin forming. The second trimester (weeks 13 through 26) is often considered the most comfortable, as morning sickness typically subsides and the baby's movements become noticeable. The third trimester (weeks 27 through 40) brings rapid growth and preparation for delivery.
Important Disclaimer
This calculator provides an estimate for informational purposes only and is not a substitute for professional medical advice. Please consult your healthcare provider for personalized guidance about your pregnancy, prenatal care, and delivery planning. Your doctor may adjust your due date based on ultrasound measurements and other clinical factors.