The purpose of this paper is to describe a new and innovative method for the calculation of societal consequences from breakdowns in critical infrastructures. Both a Social Impact Cost is calculated as lost Gross Domestic Product and non-economic consequences are quantified. For the non-economic consequences a new measure is introduced called Social Impact Magnitude that resembles the Richter scale. The paper describes the methods used and the design of the software tool developed for this purpose. The second part of the paper includes some practical examples how the societal consequences have been calculated for a number of power outage scenarios. Future potential development to cover other types of critical infrastructures and dependencies between infrastructures are indicated at the end.