This paper seeks to apply a number of biophysical sustainability metrics to an Irish city-region in order to evaluate the effect of methodological pluralism when measuring urban sustainability and to determine the outcome of using more than one method when measuring the sustainability of the same system boundary at a city-region level. It is concluded that a ‘toolkit’ approach can be useful in highlighting commonalities and differences between different metrics as well as capturing some of the deficiencies inherent in using a single biophysical metric. In addition, this paper develops an approach to measuring energy metabolism by outlining and applying the ‘energy flow metabolism ratio analysis’ methodology, which is used to measure the ratio of greenhouse gas (GHG) emissions as a function of energy material inputs.