Pregnancy Calculator
Use the Pregnancy Calculator to estimate your expected delivery date, current pregnancy week, pregnancy month and trimester. Enter the first day of your last menstrual period and your average cycle length to view an estimated pregnancy timeline.
The result is an approximate calculation. Your doctor may confirm or revise your pregnancy dates after reviewing your medical history and ultrasound findings.
Did You Know?
Only 1 in 20 babies are born on their actual due date. A normal pregnancy often lasts from 38 to 42 weeks, which keeps the majority of parents guessing right up until delivery day. Download the What to Expect app Opens a new window to track your pregnancy week-by-week!
What Is a Pregnancy and Gestational Age Calculator?
A Pregnancy and Gestational Age Calculator estimates:
- Your expected delivery date
- Your current pregnancy week
- Your approximate pregnancy month
- Your trimester
- Your gestational age
The calculation is generally based on the first day of your last menstrual period and your average cycle length. Some calculators may also use the conception date, ultrasound date or IVF embryo transfer date.
What Is Gestational Age in Pregnancy?
Gestational age refers to the number of weeks and days that have passed since the first day of your last menstrual period.
It differs from fetal age, which is calculated from the estimated date of conception. Doctors use gestational age as the standard method for scheduling scans, monitoring fetal development and planning antenatal care.
What Is an Estimated Due Date?
The Estimated Date of Delivery, or EDD, is the approximate date on which your baby may be born. It is commonly calculated by adding 40 weeks to the first day of your last menstrual period. This method usually assumes a regular 28-day menstrual cycle.
The EDD is a planning reference and not a confirmed delivery date. Labour may begin before or after the estimated date.
How Is the Estimated Due Date Calculated?
Your estimated due date may be calculated using one of the following methods:
Last menstrual period
The calculator adds approximately 280 days, or 40 weeks, to the first day of your last menstrual period.
The estimate may be adjusted according to your average cycle length.
Average cycle length
Your average cycle length can affect the estimate because not everyone has a 28-day menstrual cycle. If your cycles are usually shorter or longer, the calculation may be adjusted to better reflect the likely timing of ovulation.
Conception date
If the conception date is known, approximately 266 days are added to estimate the due date.
IVF embryo transfer date
For an IVF pregnancy, the calculation is based on the embryo transfer date and the age of the embryo at transfer.
Ultrasound dating
An ultrasound estimates gestational age using fetal measurements. Your doctor may use an early pregnancy scan to confirm or revise the calculated date.
How Does the Pregnancy Calculator Work?
The Pregnancy Calculator uses the information you enter to estimate your pregnancy timeline.
You may need to provide:
- The first day of your last menstrual period
- Your average menstrual cycle length
The calculator then applies a standard pregnancy duration of approximately 280 days. It may display your:
- Estimated due date
- Current pregnancy week
- Pregnancy month
- Trimester
The result may be less accurate if your periods are irregular or you are unsure of your last menstrual period date.
How to Use the Pregnancy Calculator
- Select the first day of your last menstrual period.
- Enter your average menstrual cycle length.
- Click Result.
- View your estimated due date and current pregnancy stage.
Check that the information entered is correct before using the result for pregnancy planning.
Why Use the Pregnancy Due Date Calculator?
The pregnancy due date calculator provides a quick estimate of your pregnancy timeline. It may help you:
- Identify your current pregnancy week
- Understand which trimester you are in
- Estimate your expected delivery date
- Plan antenatal appointments
- Track important pregnancy milestones
- Prepare for scans and tests
The result should be confirmed during a medical consultation.
What Does the Pregnancy Calculator Show?
A pregnancy calculator provides an estimated timeline based on the information you enter. Depending on the calculation method selected, it may show:
- Estimated due date: The approximate date when your baby may be born.
- Current pregnancy week: An estimate of how many weeks pregnant you are.
- Gestational age: The stage of pregnancy calculated from the last menstrual period or another relevant date.
- Trimester: Whether the pregnancy is currently in the first, second or third trimester.
- Estimated conception date: An approximate date when conception may have occurred.
- Pregnancy milestones: Key stages in the pregnancy timeline that may help you understand how the pregnancy is progressing.
These results are estimates and may differ from the dates confirmed by your doctor, particularly if your menstrual cycles are irregular or an ultrasound suggests a different gestational age.
What Can Affect Your Due Date?
Your calculated due date may vary because of:
- Irregular menstrual cycles
- Uncertainty about your last menstrual period
- Early or delayed ovulation
- An uncertain conception date
- Polycystic ovary syndrome
- Recent use of hormonal contraception
- Differences found during an ultrasound scan
- IVF or other assisted conception procedures
Your obstetrician will consider your menstrual history, ultrasound findings and treatment dates when confirming the EDD.
Track Your Pregnancy Progress
The calculator can help you check your current pregnancy week, month and trimester.
- First trimester: Up to 13 weeks and 6 days
- Second trimester: 14 weeks to 27 weeks and 6 days
- Third trimester: From 28 weeks until delivery
Use this information to understand your pregnancy stage and prepare for upcoming appointments. Follow the schedule recommended by your doctor for scans, tests and routine antenatal checks.
When Should You Visit a Doctor?
Consult an obstetrician after receiving a positive pregnancy test. The doctor can confirm the pregnancy, estimate gestational age and guide you on antenatal care.
You should also seek medical guidance if:
- You do not remember your last menstrual period
- Your menstrual cycles are irregular
- Your ultrasound date differs from the calculator result
- You conceived through IVF or another fertility treatment
- You have pain, bleeding or other pregnancy-related concerns
Frequently asked questions
How accurate is my pregnancy due date?
The due date is an estimate. Its accuracy depends on your cycle regularity, the date of your last menstrual period and available ultrasound findings. Your doctor can confirm the most appropriate date for pregnancy care.
Can I plan my baby’s due date?
You may estimate a delivery period when planning conception, but the exact date of birth cannot be guaranteed. The timing of ovulation, implantation and labour can vary.
Can the due date change during pregnancy?
Yes. Your doctor may revise the due date if an early ultrasound shows a meaningful difference from the date calculated using your last menstrual period.
What if I do not remember my last menstrual period?
Consult an obstetrician. An early ultrasound and other clinical information may be used to estimate your gestational age and due date.
How accurate is a pregnancy due date calculator?
The result is generally more reliable when your periods are regular and you know the first day of your last menstrual period. It is still an estimate and requires medical confirmation.
What factors can affect my due date?
Irregular periods, changes in ovulation timing, uncertainty about menstrual dates, IVF treatment and ultrasound findings can affect the estimated due date.
Can I use the calculator if I have irregular periods?
Yes, but the estimate may be less accurate. Entering your average cycle length may help, although an ultrasound may provide a more reliable pregnancy date.
When should I start using a Pregnancy Calculator?
You can use it after receiving a positive pregnancy test if you know the first day of your last menstrual period.
What information is needed to calculate my due date?
Most calculators require the first day of your last menstrual period and your average cycle length. Some tools may also accept conception, ultrasound or IVF transfer dates.
Does the calculator show my current pregnancy week?
Yes. The pregnancy week calculator can estimate your current gestational week. It may also show your pregnancy month, trimester and expected due date.
Why is my ultrasound due date different from the calculator result?
A calculator uses menstrual dates and an assumed ovulation pattern. An ultrasound uses fetal measurements. Differences may occur because of irregular cycles, delayed ovulation or an uncertain last menstrual period.
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Medical Disclaimer
The result shown by this Pregnancy Calculator is an approximate estimate intended for general informational purposes only. It should not be considered a confirmed delivery date, diagnosis or substitute for medical advice. The calculation may vary because of menstrual cycle irregularities, ovulation timing, assisted conception dates and individual health factors. Consult a qualified obstetrician for pregnancy confirmation, ultrasound assessment and personalised antenatal guidance.
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