calcy treasure chest of featuresLove the calculators but not the ads?

Take a sneak peek at the Ad-Free Design being enjoyed by hundreds of members for less than 25¢ a week. Full details and a bonus!

Reverse Due Date Calculator to Calculate Conception Dates

Calculator Preferences
Reverse Due Date Calculator Sign
Reverse Due Date Calculator

This extremely popular conception date calculator will calculate what date and day of the week your baby was conceived on based on your pregnancy due date. Also includes estimated dates for the missed menstrual period and for the range of days the pregnancy-causing "event" likely occurred within. Plus, you can also select any birth date -- meaning you can use the calculator to answer questions such as ...

  • When was I conceived?
  • When did I conceive my baby?
  • When to get pregnant to have a baby in April (or any other month)?
Learn More

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:Birth month:Month of birth:Pregnancy due month (or birth month):

Pregnancy due month:

Select the month of your baby's birth due date. Note that you can also select any date of birth to calculate when you or someone else was most likely conceived.

Day:Birth day:Day of due date:Pregnancy due day (or birth day):

Pregnancy due day:

Select the day of the month of your baby's birth due date. Note that you can also select any date of birth to calculate when you or someone else was most likely conceived.

Year:Birth year:Year of due date:Pregnancy due year (or birth year):

Pregnancy due year:

Select the year of your baby's birth due date. Note that you can also select any date of birth to calculate when you or someone else was most likely conceived.

Date:Conceive date:Conception date:Estimated date of conception:

Conception date:

This is 266 days subtracted from the selected pregnancy due date (the average per Naegele's Rule).

Period:Last period:Last period date:Estimated last period date:

Last period date:

This is 14 days prior to the conception date (assuming ovulation occurred on day 14 of your menstrual cycle).

If you would like to save the current entries to the secure 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.

Feedback AppreciatedFeedback Greatly AppreciatedYour Feedback Would Be Greatly AppreciatedYour Feedback Is Greatly Appreciated
Heading

Tip

Get the App!

$0.99, iPhone or Android.

iPhoneAndroid
iTunes store iconGoogle Play store icon
QR Code for Conception Date Calculator App
Help and Tools

Help and Tools:

This section, which you can Unstick or Hide in the Calculator Preferences (just above the top of the calculator), contains the following tabs (content too long to fit within bordered frame can be scrolled up and down):

About: Click this tab for an introduction to the calculator.

Instructions: Click this tab for step-by-step instructions for using the calculator.

Terms: Click this tab for a list of the descriptions that are located within each popup help button (info icons).

PCalc: Click this tab for a handy "pocket" calculator you can use when you need to calculate an entry needed for the calculator.

Data: Click this tab to save a set of entries or a note in between visits. Entries and notes will be stored to your web browser's local storage (if supported by your browser of choice), meaning they can only be recalled with the same device and web browser you were using when you saved them. If you'd like to save entries and notes between devices you can do so by subscribing to the Ad-Free Member Version.

 

Favorites

Add or remove this page to/from my favorites.

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.