Determine Key Dates with the Pregnancy Calculator

Use our handy pregnancy calculator tool to:

  • Determine the due date
  • Calculate the likely conception date
  • Calculate the end of the first and second trimesters
  • Find out how many weeks you have been pregnant
  • Calculate how many weeks you will have been pregnant on a given date
  • Calculate on which date you will be pregnant the specified number of weeks
  • Determine the likely conception date when you know the due date

Our goal is to provide you with an easily used calculator to help you quickly figure out the pregnancy dates you need to know. If you run into any problems with our pregnancy calculator, please don't hesitate to let Hannah know (through our contact form).

Using the Pregnancy Date Calculator

Enter the date of your last menstrual period and the number of days in your menstrual cycle into the pregnancy calculator, and click on the Calculate button. Other calculations are optional - use them when needed.

On average, there are 28 days in a menstrual cycle, but it can last from as little as 22 to as many as 44 days. The Pregnancy Calculator takes your menstrual cycle into account when calculating the due date and the conception date.

Also, the Pregnancy Calculator needs the number of days in your menstrual cycle when calculating the likely conception date from the given due date.

The OPT Pregnancy Calculator

  When was the first day of your last menstrual period?


*Required*  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):
Number of weeks you have been pregnant for:

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? (example: I want to see what the date will be when I am 30 weeks pregnant)

The number of weeks:

Calculated date:

Given the due date (or birth date), calculate the likely conception date (be sure to enter how long your typical menstrual cycle is first - the blank for this is up near the top of the calculator):

Calculated conception date (+/- 3 days):

Tool Copyright © 2006 C Point Pty Ltd. Improvements made by

Note: A woman can usually get pregnant during a period of 5 days each month, which is when ovulation is occurring. Typically, ovulation takes place between 12 to 16 days before your menstrual period starts. However, since sperm is able to live for 3 to 5 days within a woman's body, that makes it possible to still become pregnant even during the several days leading up to the egg's release (i.e. ovulation).

The above calculations are mathematical estimates and should not be considered infallible. If you do find any glaring errors, please don't hesitate to contact us.