While humanity seems to understand that poor quality and unsustainability are both problematic, making change happen is difficult. We examine how (T)QM could support sustainable development conceptually and then demonstrate the proposed model by assessing national sustainability improvement potential with Sweden as a case study. The work is largely conceptual. We use the Sustainability Opportunity Study (SOS) logic, with an emphasis on its Diagnosing component, in trying to Understand, Define, and Measure what national sustainability could be. (T)QM could support sustainability through system understanding, based on a Pareto guided focus on system purpose. The TQM inspired and system-based change model is named Quality for Sustainability (Q4S). It supports doing the right thing right. Q4S is defined as: Ensuring citizens’ needs are met while remaining carbon neutral and taking global responsibility for sustainability, with a focus on alleviating extreme poverty and promoting peacekeeping. The improvement potential for Swedish carbon reductions has been indicated as an example of how a complex system can be simplified to estimate a measurable improvement potential. Results provide a roadmap for understanding sustainability on a national level.