STORM Calculator

Welcome to Melbourne Water's STORM Calculator

Enter the Calculator

Enter your email address and then click 'Continue' to continue using the tool.


What do my results mean and how do I increase my rating?

Achievement of a 100% STORM rating means you have achieved a 45% reduction in the typical annual load of total nitrogen and achieved best practice objectives.

To improve your STORM rating you need to provide treatment for impervious surfaces that currently have no treatment or increase the size of existing treatments.


This calculator and/or website may be of assistance to you but the State of Victoria and its employees do not guarantee that the calculator and/or website is without flaw of any kind, or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence that may arise from you relying on any information in this calculator and/or website.


  • Dale Brown from Urban Stream
  • Ecological Engineering
  • Councils who piloted the tool: Kingston, Moreland, Port Phillip, Nillumbik, Melbourne, Bayside

Who should use STORM?

STORM is designed to be very user friendly and could be used by the general public. Typical users will be consultants, developers, architects, builders and local government staff.

What is it used for?

STORM can be used to assess whether best practice water quality objectives have been achieved for your site.

Results of STORM assessments can be submitted to statutory authorities along with development applications to demonstrate compliance with objectives.