Purpose – Preliminary sizing and optimization of propeller aircraft certified under EASA CS-23 Amendment 6 or FAA FAR Part 23. Considering relevant certification constraints and typical propulsion concepts for small aircraft. Integration of the method into a user interface known already from other tools being part of Simple Aircraft Sizing and Optimization (SAS) and PreSTo-Classic at HAW Hamburg. --- Methodology – The tool uses the proven methodology based on the Matching Chart (power-to-mass versus wing loading), the Excel-Solver and Differential Evolution (DE). Conventional propulsion: Piston engines (Otto, Otto with Turbo Compressor, Diesel) and Turboprop engines are considered. Altitude-dependent power modelling for all engines, and extended propeller efficiency calculations for variable-pitch and fixed-pitch propellers are used. The resulting tool is evaluated with the redesign of a Cessna 172. --- Findings – The existing SAS and PreSTo Excel environment known from FAA FAR Part 25 was adapted to ensure continuous user experience. The new optimization tool is "SAS-Part23-Prop". The tool reproduces the selected Cessna 172 reference parameters almost exactly. The redesign shows that consistent assumptions for propeller efficiency, rotational speed, field-length requirements, and validated statistical parameters are essential for obtaining plausible sizing results. In addition, a simple sizing tool "PreSTo-Classic-Part23-Prop" for use in the Aircraft Design lectures is available. --- Research Limitations – The results are limited by the simplified equations and statistical parameters used in preliminary sizing. No new statistical database for modern CS-23 aircraft was developed. Electric propulsion concepts are not yet included. The tool is intended for conceptual design and cannot replace detailed analysis in later design phases. --- Practical Implications – The tool provides a structured environment for students and designers to evaluate CS-23 propeller aircraft concepts, compare manual and solver-based sizing workflows, and investigate the influence of engine and propeller concepts together with matching power-to-mass and wing loading. Highly automated aircraft preliminary sizing and optimization for new and redesign is possible (SAS-Part23-Prop). Alternatively, a simple tool for hand calculations is offered (PreSTo-Classic-Part23-Prop). The tools are designed to give users a steep learning curve. --- Originality – A didactically enhanced design, redesign, and optimization tool (on preliminary sizing level) for small propeller driven aircraft is made openly available. It is especially suited for students and fills a perceived gap.