Knowing your baby’s expected arrival date is one of the most meaningful milestones in pregnancy. A Pregnancy Calculator NHS-style helps you understand your estimated due date and gestational age , and key developmental stages using medically accepted methods. If you’ve ever searched for “when is my
* Ranges from 22 to 44 days. 28 days is the average. Leave 28 if unsure.
This is an estimate based on averages. Not a medical diagnosis. Consult your doctor.
Using a pregnancy calculator is simple, fast, and requires only basic information. Here’s how it works:
Enter your last menstrual period (LMP):
This is the most common method used by healthcare providers. Our pregnancy calculator by NHS can help you determine how many weeks pregnant you are. Tools rely on this date to calculate your estimated
Enter your conception date:
If you know the exact date of conception, this can provide a more precise estimate of how many weeks pregnant you are. This is especially useful for couples who used assisted reproductive techniques like IVF.
IVF pregnancies:
Knowing the IVF transfer date can significantly influence how you calculate and select the option for a pregnancy
Use ultrasound data (optional):
You can either find your due date by checking the data from date of your last ultrasound. Early ultrasounds measure the embryo and fetal size, providing a highly accurate gestational age.
Click calculate:
The calculator instantly shows your estimated
The most common method for estimating a pregnancy
Naegele’s Rule calculates your estimated
For example, if your LMP was January 10, 2026:
This method works because, in a standard 28-day menstrual cycle, ovulation usually occurs around day 14. Conception typically happens shortly after ovulation, so counting 280 days from the LMP roughly aligns with the expected date of birth.
A pregnancy
While Naegele’s Rule is helpful for giving a general timeframe, it has some limitations:
It assumes a 28-day menstrual cycle. Women with shorter or longer cycles may have slightly different conception dates. Ovulation does not always happen exactly on day 14; early or late ovulation can shift the actual
Apart from Naegele’s Rule, doctors may use:
Early ultrasound:
An early ultrasound scan is one of the most reliable ways to estimate your pregnancy due date, especially if you’re unsure about your last menstrual period (LMP), ovulation timing, or conception date. During your first trimester, healthcare providers often use ultrasound measurements to determine gestational age more accurately than LMP-based calculations. This is why many pregnancy due date calculators include an “ultrasound” option for better precision.
However, not all pregnancies require an early ultrasound. Some doctors recommend it only in specific situations—such as irregular periods, age over 35, previous pregnancy complications, or when the due date cannot be confirmed through LMP and physical examination.
In addition to ultrasound, doctors use several pregnancy milestones to confirm your due date. These include detecting the baby’s heartbeat (usually around weeks 9–10), feeling fetal movement (typically between 18–22 weeks), and measuring fundal height during prenatal visits. The size of the uterus during early internal exams also helps refine the estimated due date (EDD). Together, these indicators ensure a more accurate and well-monitored pregnancy timeline.
Conception date: If known, this can provide a more precise estimate, especially in assisted reproductive methods.
Physical examination and fetal growth monitoring: Used later in pregnancy to confirm or adjust the
In summary, while Naegele’s Rule gives a reliable starting point, healthcare providers often combine it with other tools to provide the most accurate estimate for your baby’s arrival.
Knowing your
Several factors can influence how accurate your estimated
Menstrual Cycle Length
If your menstrual cycle is longer or shorter than the typical 28 days, your
Ovulation Timing
Ovulation doesn’t always happen on day 14. If you ovulate earlier or later than expected, it can shift the timing of conception and affect your estimated
Ultrasound Results
Early ultrasounds, especially in the first trimester, are often the most accurate way to estimate your
Multiple pregnancies
If you are expecting twins or more, the pregnancy may not follow the standard 40-week timeline, and your healthcare provider may adjust your
Pregnancy is typically divided into 40 weeks, starting from the first day of your last menstrual period. Each week represents an important stage in your baby’s growth and development. The
1-2 Weeks Pregnant
If you’re 1–2 weeks pregnant, you’re in the first month of pregnancy—just 8 months to go! Learn how pregnancy weeks, months, and trimesters are calculated to track your baby’s development accurately.
3 Weeks Pregnant: Month 1 Milestone
Congratulations! At 3 weeks pregnant, conception has occurred, and you’re in the first month of pregnancy—though it may take a few more weeks before a pregnancy test can confirm it.
This week, the tiny cluster of cells that will develop into your baby is rapidly growing. Rising hormone levels may also cause early pregnancy symptoms, such as a heightened sense of smell, one of the earliest signs that your body is preparing for this exciting journey.
4 Weeks Pregnant: Early Development and Symptoms
At 4 weeks pregnant, your body is starting to form the placenta and amniotic sac to support your developing baby.
You may notice early pregnancy symptoms this week, such as abdominal pressure and tender breasts. As the cluster of cells that will become your baby burrows into the uterine lining, some women may experience implantation bleeding. However, if you don’t notice any symptoms yet, that’s completely normal—every pregnancy progresses differently.
5 Weeks Pregnant: Month 2 Milestone
At 5 weeks pregnant, you’ve entered month 2 of pregnancy. This is the first week you can reliably take a pregnancy test, as your hCG hormone levels are high enough for a positive result. Early symptoms such as fatigue, nausea, and mild mood changes may also begin.
Meanwhile, your baby’s embryo is starting to resemble a fetus, and critical development is underway. The heart and circulatory system are forming, laying the foundation for your little one’s growth in the coming weeks.
6 Weeks Pregnant: Baby’s Early Features and Symptoms
At 6 weeks pregnant, your baby is starting to take on a more recognizable shape. The head is forming, along with the cheeks, chin, and jaws, marking the beginning of your little one’s facial development.
You may also be noticing stronger pregnancy symptoms this week, including nausea, heartburn, and frequent urination, making the early stages of pregnancy feel more real. These changes are all part of your baby’s rapid growth and your body’s adjustment to new hormone levels.
7 Weeks Pregnant: Rapid Growth and Early Symptoms
Here’s a fun fact: at 7 weeks pregnant, your embryo is now 10,000 times larger than when it first formed! Your baby is growing rapidly, with new brain cells developing at a rate of 100 per minute.
As you move into the second half of your first trimester, you may notice common pregnancy symptoms such as morning sickness, tender breasts, and food aversions. These changes reflect your body supporting your baby’s incredible early development.
8 Weeks Pregnant: Baby’s Features and Early Changes
At 8 weeks pregnant, you might not be showing yet, but your clothes may feel snug, and if you’re among the 75% of women experiencing morning sickness, you’ll definitely feel pregnant.
Your baby is growing rapidly—about a millimeter a day—and key facial features like the lips, nose, and eyelids are beginning to form. These early developments mark important milestones as your little one continues to take shape.
9 Weeks Pregnant: Fatigue and Early Development
Feeling exhausted? Around week 9 of pregnancy, fatigue is common for many moms-to-be. The main reason: your body is working overtime to develop the placenta, the vital lifeline connecting your baby to your blood supply.
This increased energy demand, along with rising hormone levels, can make you feel more tired than usual. Rest when you can—your body is supporting your baby’s rapid growth and early development.
10 Weeks Pregnant: Month 3 Milestone
At 10 weeks pregnant, you’ve officially entered month 3, and your baby has transitioned from an embryo to a fetus.
You may begin to show a small baby bump, though not seeing one yet is completely normal. Some women also notice more visible veins and increased vaginal discharge, which are typical early pregnancy changes as your body continues to adapt to support your growing baby.
11 Weeks Pregnant: Baby’s Features and Symptoms
By week 11 of pregnancy, your baby is developing distinct human features, including fingers and toes.
As you near the end of the first trimester, some moms-to-be notice that morning sickness begins to ease. However, it’s also normal to still experience nausea, food aversions, and bloating during this stage of pregnancy.
12 Weeks Pregnant: Major Milestones and Baby Bump
This is an important week for your baby: by 12 weeks pregnant, your little one’s key body systems and vital organs have formed, including those that will help fight infections and support digestion.
As you approach the second trimester, your baby bump may start to become more noticeable. If you’re not showing yet, don’t worry—your bump will grow as your pregnancy progresses
Pregnancy is divided into three trimesters, each marked by important developmental milestones, which can be tracked as you calculate your
First Trimester (Week 1–12)
This is the early stage of pregnancy when the baby’s major organs begin to form. Many women experience symptoms such as fatigue, nausea, and hormonal changes during this time.
Second Trimester (Week 13–26)
Often considered the most comfortable phase, this stage involves rapid growth of the baby. Many mothers begin to feel fetal movements, and early pregnancy symptoms may ease.
Third Trimester (Week 27–40)
This final stage focuses on the baby’s continued growth and preparation for birth. The baby gains weight, and regular medical checkups become increasingly important.
While the calculator is helpful, it should not replace professional medical advice, especially regarding your pregnancy test results.
You should consult a healthcare provider:
Regular checkups ensure both mother and baby remain healthy.
Your
Yes, you can use the calculator to find out how far along you are. Your doctor may adjust it based on ultrasound measurements or how your pregnancy progresses. Early ultrasounds, especially in the first trimester, can more accurately measure the embryo’s size and estimate gestational age. If a baby is growing faster or slower than expected, or in cases of multiple pregnancies, your
Pregnancy usually lasts between 37 and 42 weeks, with 40 weeks as the average. Only a small percentage of babies are born on the exact
If you don’t know your last menstrual period, doctors can estimate your
The Pregnancy Due Date Calculator is an essential tool for expecting parents. It provides a simple and reliable way to estimate your baby’s arrival date and track your pregnancy timeline. By understanding your due date and pregnancy stages, you can better prepare for each phase and ensure a healthy journey for both you and your baby.
NHS Pregnancy due date calculator, 21 August 2024 https://www.nhs.uk/pregnancy/finding-out/due-date-calculator/
ACOG. 2022. Methods for Estimating the Due Date. American College of Obstetricians and Gynecologists. Committee Opinion. May 2017. Reaffirmed 2022. https://www.acog.org/Clinical-Guidance-and-Publications/Committee-Opinions/Committee-on-Obstetric-Practice/Methods-for-Estimating-the-Due-Date
[Accessed January 2023]
ACOG. 2023. Prenatal Genetic Testing Chart. American College of Obstetrician and Gynecologists. https://www.acog.org/womens-health/infographics/prenatal-genetic-testing-chart
[Accessed January 2023]
American College of Obstetricians and Gynecologists, Methods for Estimating the Due Date Opens a new window, 2022.
Stanford Children’s Health, Calculating a Due Date Opens a new window, 2023.
WhatToExpect.com, Pregnancy Week-by-Week, 2023.