What is the MPN Calculator?

At PUR we test, among other water quality parameters, the amount of coliform and E. coli in water samples.  To do this, the IDEXX Quanti-Tray®/2000 is filled with a water sample which has been mixed with chemicals providing the bacteria with food and an indicator.  After incubating for 24 hours we determine the amount of coliform bacteria present by how many wells, in the tray, turn yellow.  The amount of E. coli present is determined by counting the cells that glow under a black light.  You can see these glowing cells in the photo.  You count the number of large wells that are positive and the number of small wells that are also positive.  

Once you have these two numbers you look up the final result using the IDEXX Quanti-Tray®/2000 MPN Table (per 100ml) - by looking across one row and down the appropriate column until you find the correct result.  This table is slow and a little frustrating to ensure you do not make a mistake.  At PUR, we decided that putting this into a computer program would simplify the process.  With our new software, called MPN Calculator 3.1, all one has to do is enter two numbers, hit enter, and you instantly have the correct MPN/100ml!  The same is true for the Windows Mobile version, which is now available!

The MPN Calculator is now available as an online tool!

Because of PUR's partnership with Oregon State University, the MPN Calculator is now available as an online tool, with no need for download.  If you prefer this option you can find the calculator here, on the Oregon Explorer website.

Download the Software for Windows

A new version of our software is available for download.

Please note, this software is designed for Microsoft Windows and has been tested on Windows 2000, XP, and Vista only.  Click on the link below to download the software:

Download MPN Calculator 3.1 (Windows)

Download the Software for Windows Mobile

A new version of our software is available for download.

Before you can download this software you must agree to the license agreement. Click here to proceed to the download page.

Support

To find help for any issue you may be having with our software, please feel free to e-mail us at This e-mail address is being protected from spambots. You need JavaScript enabled to view it   and we will respond in a timely manner.

Legal Disclaimer

The IDEXX Quanti-Tray®/2000 MPN Table, used to create this program, is a product of IDEXX Laboratories, Inc. IDEXX Laboratories, Inc. in no way endorses or recommends this product's use.   Partnership for the Umpqua Rivers has no affiliation or relation with IDEXX Laboratories.