How many weeks is a month pregnant?

How long is pregnancy? The short answer is 280 days, 40 weeks, 3 trimesters, or a little more than 9 months. But most women don't give birth at exactly 40 weeks pregnant, so it's impossible to know exactly how long until you meet your baby. Your due date is just a good guess – but it's helpful. So is knowing about pregnancy trimesters and how to translate weeks to months in pregnancy. (Our pregnancy weeks and months chart will help!)

How many weeks pregnant am I?

To determine your due date, healthcare providers count 40 weeks from the first day of your last menstrual period (LMP) rather than trying to guess exactly when sperm met egg. Visit our Pregnancy Due Date Calculator to check how many weeks pregnant you are.  

Healthcare providers use your LMP to date pregnancy because many women don't know which day they ovulated. And even if you know the day you had sex that resulted in pregnancy, that may not be the day you conceived: Sperm can linger in your uterus for up to five days waiting for an egg to be released so they can fertilize it.

Using your LMP to find your due date means that when you get confirmation that you're pregnant, you'll most likely be 4 or 5 weeks along. 

How many weeks are in a pregnancy?

There are 40 weeks in a pregnancy – though you're just as likely to deliver your baby a few weeks before or after that.

How many weeks are in a trimester?

Each trimester is 13 or 14 weeks long. The first trimester lasts until you're 13 weeks pregnant, the second trimester spans week 14 to week 27, and the third trimester starts the day you turn 28 weeks pregnant and lasts until week 40 (or until you deliver your baby).

How many trimesters are in a pregnancy?

There are three trimesters: the first trimester (early pregnancy), the second trimester (mid-pregnancy), and third trimester (late pregnancy).

Pregnancy weeks to month chart

Check out our chart to see how the weeks, months, and trimesters of pregnancy line up with each other.

How many months pregnant am I?

You can use the chart above to figure out how the weeks of pregnancy correspond to months. Note that you're not technically one month pregnant until after 4 weeks have passed, for example. But you are "in your first month" during the first 4 weeks and "in month nine" during the last 4 weeks.

Isn't a month four weeks long?

Actually, in a typical year, February is the only month that's four weeks (or 28 days) long. All others are either 30 or 31 days. On average, a month is 4.3 weeks, so that means the number of weeks and months of pregnancy don't match up exactly. And that's why some months in the chart are four weeks long and some are five weeks long.

Is pregnancy nine or ten months?

Forty weeks is actually a little more than 9 months. For example, if your last period started on January 1, your due date would be October 8. So that's more like nine months and one week (or even longer if you go past your due date).

So, when will I have my baby?

Your provider counts 280 days (40 weeks) from the first day of your LMP to determine your due date. But keep in mind that's just an estimate. Only 5 percent of babies are born on their due date. You're just as likely to deliver any time during the two weeks before or after that day. Your baby is considered full term between 39 and 41 weeks.

Note: Not everyone ovulates exactly two weeks after their LMP, so your due date may be adjusted if an early ultrasound indicates that your baby is more or less developed than expected.

Women who are planning to have a child expect their pregnancy to last about nine months. But many expectant fathers and mothers wonder how many weeks there are in nine months. The average pregnancy lasts forty weeks from the first day of the last normal menstrual period.

To get a more specific prediction of pregnancy duration, most physicians and midwives use a gestation calculation like the one below to provide a personalized estimate. You can use the first date of your last period or the date of conception if you know it.

Pregnancy Weeks vs. Months

Planning for a nine-month pregnancy can be confusing if you look at the total number of weeks in the average pregnancy. When you break down the numbers, it would seem that pregnancy lasts 10 months, not nine.

There are about 40 weeks in a full-term pregnancy. If you assume that a month is exactly four weeks long, that makes 10 months of pregnancy. The problem with this calculation is that it assumes that each month lasts 28 days. But most of our calendar months last 30 or 31 days.

To confuse matters even more, there is also the issue of when you actually became pregnant. While an exact date may not matter to everyone, you can estimate the date based on testing. By the time you have a positive pregnancy test, you are usually about four weeks pregnant.

The truth is that a full-term pregnancy lasts between nine and 10 months. To establish clarity about your stage of pregnancy and estimated due date, your practitioner will track your pregnancy in weeks rather than months.

Pregnancy Trimesters

While you might explain your pregnancy in weeks or months, many expectant moms also describe their pregnancy in trimesters. Each trimester lasts about 12–13 weeks. There are three trimesters in a full-term pregnancy.

First trimester

This early trimesterusuallyincludes weeks 1–13. This is considered a short trimester because many women don't know that they are expecting during the early weeks of pregnancy.

Second trimester

The middle trimester usually includes weeks 14–27. Many moms consider this to be the easiest and most comfortable trimester.

Third trimester

Your last trimester may include weeks 28–40. But many women go into labor before week 40 and some may stay pregnant a week or two longer.

Counting Pregnancy Weeks

Your practitioner will count your pregnancy in weeks to help them more accurately assess the health of you and your baby. If you are unclear about your pregnancy week, be sure to ask for your provider's guidance.

Once you get your estimated weeks of pregnancy, you can use that information and your due date to plot your pregnancy by week at home. To do this, note the day of the week that your baby is due. Then choose that day of the week in your current week of pregnancy and start counting forward.

For example, if your due date is on a Monday and you are currently in your fourth week of pregnancy, note that date on your calendar with "week 4." Then note that on the following Monday you'll be five weeks along. The Monday after that you would be six weeks along. Every Monday moving forward you gain a week of pregnancy, until around 40 weeks.

Counting Pregnancy Months

Understanding your pregnancy in weeks, months, and trimesters can be confusing enough. But you'll also be faced with plenty of pregnancy questions from others. When someone asks: how far along are you? It is usually easiest to reply in months. But the answer can vary.

There are different ways to lay out the months of pregnancy depending on whether you emphasize the first trimester or the last trimester. Here are some common breakdowns of the months of pregnancy.

Pregnancy by Month: Emphasis on First Trimester

This monthly breakdown assumes that early pregnancy is very important. Since many women aren't aware that they are pregnant during the first two weeks, month one is extended to six weeks.

• Month 1: Week 1 through week 6
• Month 2: Week 7 through week 11
• Month 3: Week 12 through week 16
• Month 4: Week 17 through week 20
• Month 5: Week 21 through week 24
• Month 6: Week 25 through week 28
• Month 7: Week 29 through week 32
• Month 8: Week 33 through week 36
• Month 9: Week 37+

Pregnancy by Month: Emphasis on Third Trimester

This weekly pregnancy breakdown includes every moment from the last normal menstrual cycle and considers the fact that some women have their babies earlier than forty weeks.

• Month 1: Week 1 through week 4
• Month 2: Week 5 through week 8
• Month 3: Week 9 through week 12
• Month 4: Week 13 through week 16
• Month 5: Week 17 through week 20
• Month 6: Week 21 through week 24
• Month 7: Week 25 through week 28
• Month 8: Week 29 through week 32
• Month 9: Week 33+

As you can see from the two schedules, there are different ways to describe which month of pregnancy you are in based on how you interpret the weeks. There is no right or wrong way to answer when people want to know how far along you are. Simply provide the week or month you feel is appropriate for your gestational age.

A Word From Verywell

Remember that when people inquire about your pregnancy progress, there is no need to explain the difference between weeks and months. Whether you answer five months or six months on the chart above, you are still 24 weeks pregnant. Simply choose the answer that best suits you.

Sometimes you might feel very pregnant and six months makes you feel better than five months. Or, perhaps you are not anxious for the pregnancy to be over and you would prefer to be five months pregnant. This mental game is one that can help you stay sane through a potentially discombobulating time.

Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

1. Eunice Kennedy Shriver National Institute of Child Health and Human Development. About pregnancy.

Additional Reading

• Jukic AM, Baird DD, Weinberg CR, McConnaughey DR, Wilcox AJ. Length of human pregnancy and contributors to its natural variation. Hum Reprod. 2013;28(10):2848-2855. doi:10.1093/humrep/det297

By Robin Elise Weiss, PhD, MPH
Robin Elise Weiss, PhD, MPH is a professor, author, childbirth and postpartum educator, certified doula, and lactation counselor.

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