Pregnancy Due Date Calculator
Estimate your baby's due date from the first day of your last period, your conception date, or an IVF transfer, and see how far along you are with the key milestones ahead.
Estimated due date
| Milestone | Week | Date |
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This is an estimate for information only, not medical advice. Your healthcare provider may adjust your due date based on an early ultrasound.
How to use the due date calculator
- Choose how you want to calculate: from the first day of your last menstrual period (the most common method), a known conception date, or an IVF embryo transfer date.
- Enter the date. If you use your last period and your cycles are usually longer or shorter than 28 days, enter your average cycle length.
- Read your estimated due date, how many weeks and days pregnant you are today, and the dates of upcoming milestones.
How due dates are estimated
Pregnancy is counted from the first day of the last menstrual period (LMP), about two weeks before conception actually happens. The standard estimate, known as Naegele's rule, adds 280 days (40 weeks) to the LMP. If your cycles are longer or shorter than 28 days, ovulation usually happens later or earlier, so the calculator shifts the date by the difference. From a known conception date the estimate is 266 days; for IVF it is counted from the transfer date and the age of the embryo.
A due date is an estimate, not a deadline. Only about 1 in 20 babies arrives on the exact day; most are born within two weeks either side. The American College of Obstetricians and Gynecologists (ACOG) defines full term as 39 weeks 0 days through 40 weeks 6 days, early term as 37–38 weeks, and late term as 41 weeks. An ultrasound in the first trimester is the most accurate way to date a pregnancy, and your provider may update your due date based on it.
The trimesters are commonly divided as weeks 1–13 (first), 14–27 (second) and 28 to birth (third). The milestones table lists commonly cited points such as the end of the first trimester, the typical window for the anatomy scan (around 18–22 weeks), and full term. Your own care plan may differ, so always follow your provider's schedule.
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Frequently asked questions
How accurate is the due date?
It is an estimate. Most babies are born between 38 and 42 weeks. An early ultrasound gives the most accurate dating.
Why does pregnancy count from my last period?
Because the date of the last period is usually known while the exact day of conception is not. That is why you are considered about 2 weeks pregnant at conception.
What if my cycle is irregular?
Dating from the last period is less reliable with irregular cycles. Use your average cycle length if you know it, and rely on your provider's ultrasound dating.
Is my information stored?
No. The calculation happens in your browser and nothing is sent or saved.