All About Due Dates

How to Make a Due Date Calculator

A due date is calculated by adding 280 days to the first day of a woman's last menstrual period.  It's not easy to do this addition on paper.  Care providers use a wheel-like device that resembles an old-fashioned circular slide rule to do this calculation.  It's a lot easier to use a computer to perform this calculation.  If you have a computer with Microsoft® Excel, you can create a simple, but completely accurate due date calculator in less than two minutes as follows:

  1. Open Excel with a new sheet.
  2. Click the cell at Column "A", Row "1" (Cell "A1").
  3. Type "Last Period:" and click Cell "A2".
  4. Type "Due Date:" and click Cell "B1".
  5. Type "14Apr02" and click Cell "B2".
  6. Type "=B1+280" and press the "Enter" or "Return" key.
     NOTE:  Don't leave out the equal sign ("=") in
            front of the expression "B1+280."

  You will see something that looks like this:
    

     
 
A
B
     
1
Last Period:  
14-Apr-02
     
2
Due Date:  
19-Jan-03
    

If you click Cell "B1," type in a different date and press the Enter or Return key, the Excel spreadsheet will recalculate the due date for the last menstrual period that you entered in cell B1.  With slight modifications to the above instructions, you should be able to make a similar Due Date Calculator using a spreadsheet program other than Microsoft® Excel.