Provisions for using the Water Demand Calculator are published in the 2018, 2021 and 2024 UPC and 2020 WE•Stand appendices. These documents contain a download link for the Water Demand Calculator.

System Requirements:

The Water Demand Calculator is a Microsoft Office Excel file and requires a compatible version of Excel 2009 or later to prevent loss of functionality. This file also uses active content (macros). When downloading this file, Microsoft Office has security features causing a message bar to appear warning that the active content may contain viruses and other security hazards that could harm your computer or your organization’s network and that the macros have been disabled. This does not mean that viruses have been detected. It only means that active content has been detected and the user is being warned. Since the source file comes from IAPMO, the file can be trusted and the macros can be enabled. You may need to change the settings in the Trust Center on your computer (find this in the Options section of Microsoft Office applications).
Once the file is trusted, the warning will no longer appear. You may also need to check with your company's System's Administrator for security permission to download a file with macros.

Enabling Macros After Downloading WDC Version 2.2

1. Download the WDC v2.2 from the IAPMO website 

2. Open the downloaded file click enable editing 

and close the security risk warning

3. Since you’re sure the file is safe and want to unblock a single file, you can unblock macros by modifying the properties of the file as follows:

  1. Open Windows File Explorer and go to the folder where you saved the file.
  2. Right-click the file and choose Properties from the context menu.
  3. At the bottom of the General tab, select the Unblock checkbox and select OK.

Flow of Algorithms

Image Courtesy of Dr. Steven Buchberger, University of Cincinnati

Water Demand Calculator


IAPMO Seeks Water Demand Calculator Task Group Members.

Interested in participating on the Water Demand Calculator Task Group?
Apply Here.


Although care has been taken to ensure the accuracy, completeness and reliability of the Water Demand Calculator (“Calculator”), neither IAPMO nor any other party makes any warranties, express or implied, or representations as to the accuracy of the Calculator. Neither IAPMO nor any other party assumes any liability or responsibility for any error or omissions in the information contained in or output by the Calculator. Neither IAPMO nor any other party assumes any responsibility for the consequences of use of such information, nor for any infringement of third party intellectual property rights which may result from its use.

Please email any comments on the calculator to Dan.Cole@IAPMO.org