Due Date Calculator
Estimate your pregnancy due date from your last menstrual period or conception date. Visualize your trimester timeline and key milestones.
Enter Your Last Menstrual Period
Select the first day of your most recent menstrual period.
A typical cycle is 28 days. Adjust if your cycle is shorter or longer (20-45 days).
Advertisement
How to Use the Due Date Calculator
Our due date calculator helps you estimate when your baby will arrive based on either the first day of your last menstrual period (LMP) or your known conception date. Simply select a calculation mode, enter the relevant date, and the calculator instantly provides your estimated due date along with a visual trimester timeline, key pregnancy milestones, and your current gestational age.
The most common method for calculating a due date 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 menstrual cycle with ovulation occurring on day 14. If your cycle is shorter or longer than 28 days, you can adjust the cycle length in the calculator to get a more accurate estimate. The calculator automatically accounts for this difference by adjusting the ovulation date accordingly.
If you know your conception or IVF transfer date, you can switch to Conception Date mode, which adds 266 days (38 weeks) from the date of conception. This method can be more accurate when the conception date is precisely known, such as with IVF procedures.
The reverse calculator mode lets you enter a known due date to work backward and determine the estimated conception date and last menstrual period. This is helpful if your healthcare provider has already given you a due date based on an ultrasound and you want to understand the corresponding dates.
Pregnancy is divided into three trimesters. The first trimester (weeks 1-12) is a critical period of early development when the baby's major organs begin forming. The second trimester (weeks 13-26) brings rapid growth and the first noticeable fetal movements. The third trimester (weeks 27-40) is when the baby gains significant weight and prepares for birth. Our visual timeline helps you see exactly where you are in your pregnancy journey.
Important: This calculator provides estimates only and should not replace professional medical advice. Only about 4-5% of babies are born on their exact due date, and a full-term pregnancy can range from 37 to 42 weeks. Always consult your healthcare provider for personalized guidance throughout your pregnancy.
Frequently Asked Questions
How is a due date calculated?
A due date is most commonly calculated using Naegele's rule, which adds 280 days (40 weeks) to the first day of your last menstrual period (LMP). If you know your conception date, the due date is 266 days (38 weeks) from conception. Both methods estimate the same delivery date, since ovulation typically occurs around day 14 of a 28-day cycle.
What is Naegele's rule?
Naegele's rule is a standard method for estimating a pregnancy due date. It works by adding one year to the first day of your last menstrual period, subtracting three months, and adding seven days. This is mathematically equivalent to adding 280 days (40 weeks) to your LMP date. The rule assumes a 28-day menstrual cycle with ovulation occurring on day 14.
How accurate are due dates?
Only about 4-5% of babies are born on their exact estimated due date. Most babies are born within one to two weeks before or after the due date. A pregnancy is considered full-term between 37 and 42 weeks. Factors such as cycle length, the accuracy of your LMP date, and individual biological variation can all affect accuracy.
What are the three trimesters of pregnancy?
Pregnancy is divided into three trimesters. The first trimester spans weeks 1 through 12, during which major organs begin forming. The second trimester covers weeks 13 through 26, when the baby grows rapidly and movements become noticeable. The third trimester runs from week 27 through week 40, as the baby gains weight and prepares for birth.
Can my due date change during pregnancy?
Yes, a due date can be adjusted based on ultrasound measurements, especially during the first trimester when dating is most accurate. If there is a significant discrepancy between the ultrasound date and the LMP-based date (usually more than 7 days), your healthcare provider may revise the due date. Later ultrasounds are less reliable for dating.