Gestational Age Calculator

Pregnancy, also known as gestation, occurs when the egg is fertilized by the sperm after it is released from the ovary. Once you find out that you are pregnant, there are a lot of things you need to know – like the exact date your child will enter this world. The gestational period is about 270 days, i.e., 9 months. To make this journey more safe and reliable, we have come up with this simple calculator that helps you know the age of little one, week by week, and month by month.

Current Date

Average Length of Cycle


The First Trimester (weeks 1-12): -
The Second Trimester (weeks 13-27): -
The Third Trimester (weeks 28-40): -
Your Safe Range To Give Birth Is Between:

Significant Milestones in Embryo/Fetal Development

Your baby is conceived
Week 2
Positive pregnancy test
Week 4
Organs begin to form, heart starts beating
Week 5
Major organs have formed, heart can be heard
Week 10
Second trimester, risk of miscarriage decreases
Week 12
Now is a good time to announce your pregnancy
Week 14
Your baby can now see light
Week 15
Your baby's gender is visible on ultrasound
Week 16
You can feel your baby move around
Week 18
Your baby can now hear sounds
Week 19
Premature babies have a chance to survive
Week 23
Third trimester, your baby can breathe
Week 27
Fingernails and toenails have formed
Week 32
Your baby is now considered full term
Week 37
Your baby is due any time now!
Week 40

Multiples - Due Dates by Average Gestation

37 weeks
33 weeks
32 weeks
First TrimesterSecond TrimesterThird Trimester
Week 1:
Week 13:
Week 28:
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Week 14:
Week 29:
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Week 15:
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Week 31:
Week 5:
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Week 32:
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Week 18:
Week 33:
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Week 19:
Week 34:
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Week 35:
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Week 21:
Week 36:
Week 10:
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Week 37:
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Week 38:
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 Week 25:
Week 40:
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 Week 27:
Week 42:

What Is The Pregnancy Due Date Calculator?

This pregnancy due date calculator helps in estimating the expected due date, also known as EDD. Usually, the EDD is 280 days from the first day of the last menstrual period (LMP) (1).

How To Calculate The Pregnancy Due Date

For women with a regular menstrual cycle, ovulation happens at about 11-21 days after the first day of the last period. Since most women are unaware when ovulation happened, their first day of the last menstrual period is taken into account to get the due date.

Using the pregnancy due date calculator is very simple.

To use the Gestational Age Calculator, you simply need to enter the first day of your last period and also the current date when you are using it. The tool will calculate 40 weeks from the first day of your last menstrual period and gives you the due date.

How Is It Useful?

This simple due date calculator will help you estimate the date of your baby’s arrival.

This gestational age calculator is a general guide for expecting mothers as no two pregnancies are the same. Sometimes, the babies arrive sooner or later than compared to the expected due date.

If you are pregnant, this calculator helps you keep track of your due date and monitor the progress of your pregnancy. It also gives the mother enough time to be prepared for the little one.

This is perhaps very helpful for pregnant females and practicing gynecologists. This gives us a rough estimate about the baby’s age and an idea about the delivery to happen.

Does Cycle Length Affect Due Date?

Yes, your due date can change due to irregular periods or having cycles of more than 28days. But it's nothing to worry about. A lot of women experience hormonal imbalances and nutrient deficiencies, which results in delayed periods and affects the due date.

If you have regular periods, you can get to know the exact due date, but if you have cycles of about 35 days, follow this simple calculation to get estimated due date (EDD).

For example, if your menstrual cycle is 35 days long, and your first day of period was December 1:

  • Add 21 days (December 22).
  • Subtract 14 days to find your adjusted LMP date (December 8).
  • Enter this date in the calculator to get your gestational age or expected due date.

Can The Due Date Change In The Third Trimester?

Yes, and it depends on a multitude of factors. Your healthcare provider will recommend a health check-up every two weeks to know the progress of your pregnancy.

The doctor might suggest an ultrasound scan and change the due date based on the findings like low levels of fluid around the baby, if the baby is actually too small or bigger for the gestational age, or underlying issues in the pregnancy like gestational diabetes, hypertension, etc. If your baby is extra large for the gestational age, the doctor might recommend early delivery.

How Accurate Is Your Due Date By Ultrasound?

Ultrasound examinations done in the initial stages, i.e., from 12 -22 weeks, are accurate and match the due date (2). However, ultrasound scans performed after 22 weeks of gestation are not reliable and cannot be used to estimate the baby’s arrival because the size of the baby does not reflect the age. Even an average baby differs by 2-3 weeks of age due to growth. Ultrasound performed at 12 weeks of gestation is most accurate and reliable, with a difference of 10 days for the due date (2).

The journey from conception to delivery is beautiful, and it should be handled with great care. This gestational age calculator is a simple tool to calculate your due date, but one cannot completely rely on this. Go through all the tests and scans advised by the doctor to know the progress of the fetus.

Did you know that only about 4% of babies are born on their due date? Although this tool will give you a rough idea of when to expect your baby, the baby will arrive when he/she is ready.

Frequently Asked Questions

Is gestational age the actual age?

Yes, gestational age is the actual age. It is measured from the first day of the last menstrual cycle to the present date.

Do doctors go by gestational age or fetal age?

Doctors go by gestational age as it is more accurate compared to fetal age.

What if fetal age is less than gestational age?

If the fetal age is less than gestational age, it may indicate the baby’s low birth weight.


1. Estimated Date of Delivery (EDD), StatPearls, US National Library of Medicine, National Institutes of Health.

2. Pregnancy Dating, StatPearls, US National Library of Medicine, National Institutes of Health.

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