The question ‘how much is enough?’ can be related to two different kinds of thresholds: minimum and maximum levels. Two separate discussions on these levels are held within two different research fields – abstract justice theory and practical environmental science – and both use the term ‘sufficiency’ to denominate their subject. The discussion in each research field is concentrated almost exclusively on either minimum or maximum levels. It is argued instead that both are closely linked to each other and that the combination of both types of thresholds actually results in what the concept of sustainability demands. The aims here are to bring these two sufficiency debates together and to explore conceptual links as well as differences.