Pregnancy Due Date Calculator
Pick the first day of your last period and we’ll estimate your due date and how far along you are today.
What the estimate means
Pregnancy dating counts from the last period rather than conception, which is why you are already “4 weeks pregnant” around a missed period. The due date marks 40 completed weeks, and it is the center of a window rather than a deadline.
Knowing your week matters mostly for what comes with it: screening windows, scan timing, and, once your baby arrives, the first-year rhythm our month-by-month guides walk through.
The trimester also sets the other number people look up, how much weight to gain. Our pregnancy weight gain calculator gives the recommended range for the whole pregnancy from your BMI before it began.
Frequently asked questions
The standard estimate (Naegele’s rule) adds 280 days, 40 weeks, to the first day of your last menstrual period, adjusted for your average cycle length. An early ultrasound can refine the estimate, and providers treat that dating as the more reliable one.
It is an estimate, not an appointment. Only around 1 in 20 babies arrives on the due date itself; most are born in the two weeks around it. Full term spans 39 to 40 completed weeks.
With irregular cycles the last-period method gets less reliable, because ovulation timing shifts. The cycle slider helps a little, but an early ultrasound is the accurate way to date the pregnancy; ask your provider.
Pregnancy is commonly divided into three trimesters: roughly weeks 1 to 13 (first), 14 to 27 (second) and 28 to birth (third). The calculator shows which trimester you are in today and how far along you are.
From due date to day one
When your baby arrives, Growbaby picks up where the countdown ends: adaptive soothing for the newborn nights, Growy for the 2 AM questions, and a growth journal from the very first day.
This tool is for general informational purposes only. It is not a medical device and does not provide medical advice, diagnosis or treatment. Due date estimates from period dates are less reliable with irregular cycles; ultrasound dating by your provider takes precedence. For any question about your or your baby’s health, always consult a qualified healthcare provider.
