MPN Calculator

The MPN Calculator 3.1 determines the most probable number (MPN) based on the IDEXX Quanti-Tray®/2000 MPN Table for 100 ml samples. To use this tool, please enter the number of large cells on the Quanti-Tray that are positive in the first box. Then enter the number of small cells on the Quanti-tray that are positive in the second box. Then either click the "Find MPN" button or hit the enter key on your keyboard. The MPN will then be displayed in the box labeled ""MPN".

Large Positive Wells: (0-49)
Small Positive Wells: (0-48)

The MPN Calculator 3.1 is also available for download at:

The MPN Calculator 3.1 is provided for informational purposes only. This calculator is shared with permission from IDEXX Laboratories, Inc. 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. The Partnership for the Umpqua Rivers has no affiliation or relation with IDEXX Laboratories. While this tool has been checked for accuracy, no guarantees are expressed or implied. The MPN Calculator 3.1 is provided as is.

For IDEXX’s MPN Generator software program (mpn32.exe), which calculates the most probable number and lower and upper 95% confidence limits, please go to

The MPN Calculator 3.1 was created by Kris Lyon of the Partnership for the Umpqua Rivers. For comments, questions, or help please e-mail Or you can visit us at