Baby Due Date Calculator to Calculate Pregnancy Due Dates

Baby Due Date Calculator Sign

This online pregnancy due-date predictor will determine the due date and conception date based on the first day of your last menstrual period -- including what day of the week the due day falls on.

Plus, this due date estimator will also generate a list showing the dates of each of the 40-weeks of pregnancy so you can keep track of how many weeks pregnant you are.

And finally, the results also include a Pregnancy Weeks Meter to give you a visual reference as to how far along you are in your pregnancy term.

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Frequently searched pregnancy due dates:

  • 40 Weeks from Today:
  • 40 weeks from Valentine's Day:

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Baby Due Date Calculator

Calculate pregnancy due date, including the day of the week, and see how many weeks along you are.

Special Instructions

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Selected Data Record:

A Data Record is a set of calculator entries that are stored in your web browser's Local Storage. If a Data Record is currently selected in the "Data" tab, this line will list the name you gave to that data record. If no data record is selected, or you have no entries stored for this calculator, the line will display "None".

DataData recordData recordSelected data record: None
Month:Month last prd:Month of last period:Month of last menstrual period:

Month of last period:

Select the month containing the first day of your last menstrual period.

Day:Day last prd:Day of last period:Day of the month of last menstrual period:

Day of last period:

Select the day of the month of the first day of your last menstrual period.

Year:Year last prd:Year of last period:Year of last menstrual period:

Year of last period:

Select the year containing the first day of your last menstrual period.

Conc date:Conceive date:Conception date:Estimated date of conception:

Estimated conception date:

This is 14 days after the start of your last menstrual cycle as the baby due date calculator assumes you ovulated on Day 14 of your menstrual cycle (the average per Naegele's Rule)

Due date:Est due date:Estimated due date:Estimated baby due date:

Estimated due date:

This is 280 days since the first day of your last menstrual period (ovulation on day 14 of cycle plus 266 days for average human gestation period).

Weeks:Weeks:Weeks pregnant:Number of weeks pregnant:

Number of weeks pregnant:

This is an estimate of how many weeks along you are in your pregnancy.

If you would like to save the current entries to the secure online database, tap or click on the Data tab, select "New Data Record", give the data record a name, then tap or click the Save button. To save changes to previously saved entries, simply tap the Save button. Please select and "Clear" any data records you no longer need.

Help and Tools


How to calculate due dates, when 40 weeks from a date is, and due date based on weeks pregnant.

How to Calculate Due Date

The formula most often used to calculate a baby's due date is based on a calculation developed by a German obstetrician Dr. Franz Naegele back in the 1850s. Hence the formula is often referred to as Naegele's Rule.

Dr. Naegele's studies concluded that the average length of time between conception and a baby's birth was 266 days. His studies also showed that the average ovulation occurred 14 days from the first day of a woman's last menstrual period. Therefore your baby's due date can be estimated by adding 280 days (14 + 266) from the first day of your last menstrual period.

Or, using a shorthand method, you can also estimate your baby's birth date by adding 7 days to the first day of your last period and then subtracting 3 months from the result to get the month and day of the due date.

For example, if the first day of your last menstrual period was April 7th, your estimated due date would be January 14th (4/7 + 7 days = 4/14, minus 3 calendar months = 1/14).

40 Weeks Calculator

Use the following to calculator to add or subtract 40 weeks (280 days, or 9.20547 months) to or from a given date.

40 Week Calculator

Due Date Based on Weeks and Days Along

If you know how many weeks and days you are along, but not the due date, the following calculator will estimate your due date based on weeks and days along.

Due Date Calculator Based on Weeks and Days
Weeks along:
Plus days:
Due date:

Adjust Calculator Width:

Move the slider to left and right to adjust the calculator width. Note that the Help and Tools panel will be hidden when the calculator is too wide to fit both on the screen. Moving the slider to the left will bring the instructions and tools panel back into view.

Also note that some calculators will reformat to accommodate the screen size as you make the calculator wider or narrower. If the calculator is narrow, columns of entry rows will be converted to a vertical entry form, whereas a wider calculator will display columns of entry rows, and the entry fields will be smaller in size ... since they will not need to be "thumb friendly".

Show/Hide Popup Keypads:

Select Show or Hide to show or hide the popup keypad icons located next to numeric entry fields. These are generally only needed for mobile devices that don't have decimal points in their numeric keypads. So if you are on a desktop, you may find the calculator to be more user-friendly and less cluttered without them.

Stick/Unstick Tools:

Select Stick or Unstick to stick or unstick the help and tools panel. Selecting "Stick" will keep the panel in view while scrolling the calculator vertically. If you find that annoying, select "Unstick" to keep the panel in a stationary position.

If the tools panel becomes "Unstuck" on its own, try clicking "Unstick" and then "Stick" to re-stick the panel.