Increasing the specific energy, energy density, specific power, energy efficiency and energy retention of electrochemical storage devices are major incentives for the development of all-solid-state batteries. However, a general evaluation of all-solid-state battery performance is often difficult to derive from published reports, mostly due to the interdependence of performance measures, but also due to the lack of a basic reference system. Here, we present all-solid-state batteries reduced to the bare minimum of compounds, containing only a lithium metal anode, β-Li₃PS₄ solid electrolyte and Li(Ni_0.6Co_0.2Mn_0.2)O₂ cathode active material. We use this minimalistic system to benchmark the performance of all-solid-state batteries. In a Ragone-type graph, we compare literature data for thiophosphate-, oxide-, phosphate- and polymer-based all-solid-state batteries with our minimalistic cell. Using fundamental equations for key performance parameters, we identify research targets towards high energy, high power and practical all-solid-state batteries.