Health and Fitness / Free Tools
Free Pregnancy Due Date Calculator Online
Use this free pregnancy due date calculator to estimate your baby's due date, current week of pregnancy, and trimester based on your last menstrual period, conception date, or IVF transfer date. It works as a general pregnancy calculator and shows your progress at a glance - no sign-up required.
What is a pregnancy due date calculator and why it matters
A pregnancy due date calculator estimates when a baby is likely to be born, based on the date of the last menstrual period, a known conception date, or an IVF transfer date. This matters because knowing an estimated due date helps with scheduling prenatal appointments, tracking fetal development milestones, and general planning - even though actual birth dates vary naturally by up to two weeks in either direction.
How this calculator works
The most common method, based on the last menstrual period, uses Naegele's rule: adding 280 days (40 weeks) to the first day of the last period, with an adjustment if your average cycle length isn't the standard 28 days. If conception date is known, 266 days (38 weeks) is added instead, since conception typically happens about two weeks after the last period. For IVF pregnancies, the due date is calculated from the transfer date plus the known embryo age at transfer, which gives a more precise starting point than LMP-based methods.
Common searches this calculator answers
- When is my baby due?
- How many weeks pregnant am I?
- What trimester am I in?
- How is a due date calculated from my last period?
- How do I calculate my due date from an IVF transfer date?
How to use it
- Choose the calculation method that matches what you know: last period, conception date, or IVF transfer date.
- Enter the relevant date.
- If using last menstrual period, enter your average cycle length if it isn't 28 days.
- Click Calculate due date.
- Read your estimated due date, current week, trimester, and days remaining.
Tips
- An ultrasound in the first trimester is generally the most accurate way to confirm a due date - use this calculator as a starting estimate, not a final answer.
- If your cycles are irregular, the last menstrual period method is less reliable - a conception date or early ultrasound will give a more accurate result.
- Due dates are estimates, not deadlines - full-term birth is considered anywhere from 37 to 42 weeks.
- Keep track of your week-by-week progress to know which prenatal milestones and tests are typically scheduled around that time.
Frequently asked questions
Is this pregnancy due date calculator free to use?
Yes. It is completely free, works in your browser, and does not require any sign-up or download.
How accurate is a due date calculated this way?
It is a standard estimate used widely in obstetrics, but only a small percentage of babies are born exactly on their calculated due date. Most births happen within about two weeks before or after the estimate.
Why does cycle length matter for the last menstrual period method?
Ovulation timing shifts with cycle length. A cycle longer than 28 days generally means ovulation happens later, which shifts the estimated due date later as well, and vice versa for shorter cycles.
Why is the IVF method considered more precise?
With IVF, the embryo transfer date and embryo age are precisely known, removing the guesswork around ovulation timing that exists with the last menstrual period method.
Can my doctor give a different due date than this calculator?
Yes. Doctors often adjust the estimated due date based on ultrasound measurements, particularly from the first trimester, which can be more accurate than date-based calculations alone.