Please tell us the first day of your Last Menstrual Period (LMP).



It can be a little complicated trying to understand and follow your doctor as they plot out your pregnancy and show you when you likely conceived and when you are due. This pregnancy calculator will help you to see the numbers and work out all of the relevant dates for you.

The average gestation period for a human baby is around 280 days, which is approximately 40 weeks. This works out to around nine months, but counting each week is more accurate and gives you a better indication of how your baby’s development is progressing. The gestational period will also differ depending on a variety of factors, including the physical state of both the mother and the baby.

Use our pregnancy calculator to help get an idea of where you are in the gestational period and what to expect moving forward.

How to use our pregnancy calculator

The one element of your menstrual cycle that you can track for sure is the first day of menstruation. The pregnancy calculator uses this date to work out when you likely conceived and how far along you are in the gestational process.

It may seem odd at first to use your previous menstrual period as the start date for your pregnancy. However, it is very common to work forwards from that date and count the weeks from there.Since it’s difficult to track the exact date of fertilization and implantation, going by the start of your previous menstrual period is the best method for calculating.

What if you don’t remember the first day of your last menstruation?

Many women don’t track their menstrual periods exactly. This is usually only something women do if they are actively trying to get pregnant. The good news is, you can use an approximate date for your menstrual period and still get a fairly accurate calculation.

No one’s body is the same, so the information you get from the pregnancy calculator is based on averages. This is why an approximate start date will work just fine.

It’s important to note that if you have a long cycle, it can be a lot harder to get accurate information on your pregnancy. This is because the extra time before you ovulate can throw out the calculations slightly.

To be completely sure about how far along you are, it’s best to go for an ultrasound with your gynecologist. This will give you the most accurate information.

Can the pregnancy calculator work on an irregular cycle?

As with a long cycle, an irregular cycle does make it harder to calculate your conception date. This is because the date of your ovulation changes, which means that your fertile period and your menstrual period start at different times each cycle. However, you can still use the pregnancy calculator to get an idea of where you are in the gestational process.

When using the pregnancy calculator, go for an average in terms of your cycle length. This will give you a good idea of where you are in the gestational process.

Remember, the pregnancy calculator can be used to give you a range of information. It will tell you your conception date, due date, when you’re likely to feel the baby move and help you to work out what to expect at each stage of gestation.

Why is a pregnancy counted in weeks?

Most of us grow up knowing that a normal pregnancy is nine months. However, when you fall pregnant and go to the doctor, you’ll find that everything is counted in weeks rather.

The starting point for your pregnancy is always considered to be the first day of your last menstrual period. From this day onwards, you count in weeks. Every four weeks is another month in your pregnancy. At the end of twelve weeks, you have finished your first trimester and are now in the second trimester.

The reason doctors count in weeks and don’t go by normal calendar months is because of how rapidly babies develop. Each week you can expect something new, and counting in months just isn’t accurate enough. Additionally, calendar months aren’t all the same in terms of length – varying from 28 days to 31 days. By counting in specific weeks, you can get a more accurate calculation on both your conception and due dates.

Readers’ questions:

How do I calculate how far along I am in my pregnancy?

It can be quite a complex question to answer, which is why we’ve created our pregnancy calculator to help out. It works based on an average menstrual cycle of 28 days and uses the first day of your last menstruation to work out when you conceived. It’s not 100% precise, but gives you a good approximation.

When do I start counting the weeks of pregnancy?

Your doctor will start counting from the first day of your last menstruation, making this week one. Every four weeks from this point on is considered a month of pregnancy.