Ongoing climate crisis increase people's outdoor thermal stress, discouraging outside activities and intensifying indoor consumptions. Amelioration of urban microclimates is necessary to safeguard citizens from thermal strokes without energy-intensive strategies, ensuring future cities' sustainable development. More than 200 calculation methods can be adopted with the purpose to design thermally comfortable public spaces, but existing literature lacks selection criteria to justifiably choose the appropriate ones. As resolution, the Metamatrix of Thermal Comfort has been developed. It's a graphical methodology, addressed to academicians and practitioners, that allows to rapidly comprehend and compare the specificities of 65 renowned thermal comfort indices and thermo-physiological models, explaining their mutual interactions. To promote practicality in thermal comfort studies, relying on calculation tools, an Operational version, including only 22 indices and models integrated in computer programs, is presented. A qualitative evaluation by approximately 30 criteria, such as climatic and physical factors, meteorological conditions, solar exposure and type of environment, allows to select thermal comfort calculation methods compatible to specific needs. To find appropriate computational tools, the Metamatrix of Software can be consulted. An application example is provided, proving the suitability of this graphical methodology as a powerful asset to apply outdoor thermal comfort-driven design to urban planning.