Due Date Calculator

Our due date calculator is simple to use and gives you a good idea of when to expect your baby. Remember, a “due date” doesn't tell you exactly what day your baby will arrive. It's better to think of it as a loose estimate.

an eviction notice on the due date calculator banner

It's generally considered “safe” for your baby to come when you are between 37 and 42 weeks pregnant. This gives a five week range to look for your baby's birthday! With a healthy pregnancy you'll probably carry your baby to 40 weeks, and first time mothers are especially likely to go over their due date. Babies born at 39, 40, and 41 weeks are usually the healthiest – there is a lot of brain and bone development that occurs between 36 and 40 weeks.

Some women like to say a general rather than a specific date. For instance they say “I'm due in late August” instead of “August 25th.” You can even say your due date is a month later than it truly is! This may seem strange, but it won't when you're close to your due date and everyone keeps saying “you haven't had that baby yet?!”

Just remember, your due date is an estimate and not set in stone. Expect your baby will be born sometime around his or her due date but probably not on it!

Pregnancy Calculator

When was the first day of your last menstrual period?


Number of days in your menstrual cycle
Likely conception date:
End of first trimester (12 weeks):
End of second trimester (27 weeks):
Your due date is (40 weeks):
(1) Fetal age (from the conception date):
(2) How far along you are in your pregnancy:
How many weeks will you be pregnant on a given date?


Number of weeks you will be pregnant for:
On which date will you be pregnant for the given number of weeks?
the number of weeks:
Calculated date:
Given the birtdday or due date, calculate likely conception date


Calculated conception date:

(NOTE: Trying to balance your pregnancy, life, and getting ready for baby? Use my checklist pack stay healthy (naturally), organized, and confident throughout your pregnancy! Get them here.)

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Factors Included on the Due Date Calculator

  • Last Menstrual Period:This is the very first day of your last period. Put in the date that your last period started. If you didn't write it down, get out a calendar and look it over. It may help for you to remember what was going on when you started your last period – then you may be able to recall the date you need.
  • Average Length of Cycles:How long do your periods usually last? The “average” is 28 days. But your cycle might be longer or even a little shorter. This can change your due date, so enter your cycle length if you know it. If your cycles are irregular or you do not know how long they usually are, use the default of 28 days.
  • Average Luteal Phase Length:The Luteal Phase is the time after ovulation to the beginning of your next period. If you chart your temperatures you'll know how long your luteal phase is because it's on your charts. You may also know if you use any method of tracking ovulation occurrence. Many women don't really know the length of the luteal phase. It defaults to 14 days (which is the average).

The Due Date Calculator gives you good estimates of three dates. Date of conception is the date that your baby was probably conceived. This date is approximately two weeks after your last menstrual period. Due Date is the approximate date for when your baby will make his or her arrival. Remember this is just an estimate. Estimated fetal age tells you about many weeks of development your baby has reached.

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