Pregnancy Calculator
Calculate your pregnancy week and estimated due date by entering your last menstrual period.
How is Pregnancy Week Calculated?
Pregnancy week is determined by counting from the first day of the last menstrual period (LMP). According to this method, pregnancy duration is accepted as 40 weeks (280 days). However, this date is only an estimated due date; delivery usually occurs around this time.
Enter your last menstrual period to calculate your pregnancy information.
Important Warning: This calculation tool is for informational purposes only and does not replace medical diagnosis. Please consult a gynecologist for accurate pregnancy dating and follow-up. Ultrasound measurements can provide more accurate results.
What You Should Know About Pregnancy Calculation
How is gestational age calculated?
Gestational age is counted from the first day of your last menstrual period (LMP). On this basis pregnancy is taken as 280 days, or 40 weeks. Counting starts from the LMP rather than the day of conception, which is why you are already considered two weeks pregnant at the moment of fertilisation.
The method assumes a regular 28-day cycle with ovulation on day 14. If your cycle differs, the calculated week may deviate from your true gestational age.
Is the estimated due date exact?
No. The due date is a reference point, not a target. Birth before or after this date is normal; deliveries between 37 and 42 weeks are considered term.
The date is used to time antenatal tests, assess fetal growth and plan delivery when needed. On its own it is not a promise.
If you do not know your last period date
Not remembering the date is common and not a problem. In this case gestational age is established by ultrasound, and measurements taken in the first trimester are the most reliable method.
Dating is also left to ultrasound for pregnancies conceived while breastfeeding or shortly after stopping contraception.
If your cycles are irregular
If your cycle is noticeably longer than 28 days, ovulation happens later and an LMP-based calculation will overstate the gestational age. This gap can be wider in conditions such as polycystic ovary syndrome.
A difference between the calculator and the ultrasound is therefore expected, and the ultrasound measurement takes precedence.
Calculation in IVF pregnancies
LMP is not used in IVF pregnancies. Dating is based on the embryo transfer date and the age of the transferred embryo, which is more precise because it relies on known data.
Your clinic will already have given you your gestational age and due date; this calculator may be misleading for IVF pregnancies.
Trimesters
Pregnancy is divided into three periods. The first trimester (weeks 0-13) is when organs form and nausea and fatigue are most noticeable. The second trimester (weeks 14-27) is when most women feel best and fetal movements begin to be felt. The third trimester (from week 28 to birth) is when the baby grows rapidly and preparation for delivery takes place.
Each period has its own monitoring and tests, which is why knowing your gestational age matters for regular follow-up.
Does the calculator replace an examination?
It does not. This tool only helps you see your timeline. Whether the pregnancy is inside the uterus, how the baby is developing and the mother's health can only be assessed by examination and ultrasound.
If you have bleeding, severe abdominal pain, fever or dizziness, contact your doctor without waiting.
Frequently Asked Questions
We'll Call You
Get in touch quickly via WhatsApp
