Index IntroductionPurpose of the StudyStudy MethodEffective Factors in CategorizationFloor Area Ratio (FAR) is one of the main characteristics of urban area, which is always considered by urban planners . This issue has become one of the main bases of urban development policy in Iran in recent years and has been emphasized through the framework of numerous urban development plans. Therefore, a fundamental vision in this regard is mandatory. The most important achievement of the current century in the field of urban development is the consideration of citizens' rights and qualitative aspects in this regard. Unprofessional interference such as the sale of excessive FARs and uncontrolled and unplanned developments, especially for housing purposes, have occurred in most large cities without considering the variability and difference of urban land and simply to obtain earnings for the municipality and profitability of a limited group of investors, which has resulted in a worsening of the quality of the urban environment and a lack of sustainability in the field of environmental safety, health and comfort of citizens. Whereas the effect of tall buildings on urban areas and citizens in terms of physical, economic, social, urban development, etc. is undeniable, therefore special attention to urban development laws is necessary. The scope of this study includes recognizing the implementation of urban laws related to FARs and controlling urban development by examining laws on FARs and tall building construction in some sample countries around the world, to identify variable solutions and adapted using global experiences. In the end, studying Tehran and New York, as two modern cities with more or less similar conditions and comparing the laws and ways of dealing with the problems of urban development and FARs, we understand the level of success of each of them in this regard and which are the most suitable solutions. The study method in this article is combined, so that, using the research method and basic documented and library studies, relevant information is collected and further examined using quantitative and qualitative methods. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an original essay IntroductionAlmost all developed and developing countries face serious problems due to the rapid and vertical growth of cities in recent decades. The issues related to this phenomenon have not only widely influenced urban development policies, but also its consequences have played an important role in the economic, social, political, managerial and environmental issues of societies. Concerns about this phenomenon made developed countries, especially during World War II, take certain measures to resolve or control this crisis. The main bases of these measures include policies on the construction of tall buildings, mass development, modification of tax laws, promulgation of land laws for optimized use, improvement and renovation of old and central urban areas, plans for land preparation of new localities, development of new cities, and above all, a policy of increasing the population density and FAR of cities. Through examining many of these policies, one can perceive the undeniable role of the FAR component in shaping the physical appearance and shape of the city. In these plans, the FAR is determined by considering the population expected for the horizon of the plan and the policies of urban development and urban regions, as well asconsidering environmental capabilities, urban infrastructure services and facilities and social, economic and cultural characteristics. Therefore, it is essential to focus on the important role of housing in the city and urban planning, focus on the position of FAR in projects, its role and importance in the organization of the urban area, the factors and criteria that influence the itself and the legal discussion in this regard. Various limitations existing in a city result in restrictions on the admission of population for that city and its suburbs, when due for the same reason, the legislation on the level of construction permitted in urban development plans is known and therefore owners are prohibited from constructing excessive buildings considering their building permits. Purpose of the study Identify the factors that influence FARs Clarify the concept of FAR as an urban development tool for housing projects Study questions What are the effective criteria for determining FARs? Can effective criteria in modern urban design be achieved by considering the common legal aspects of FARs in the countries studied? Study method Considering that this article is analytical, quantitative and qualitative in nature and the data collection was fulfilled through the research method and documentary and library studies, which were further explored, therefore, the study method in this article is combined type. Position of FAR in the Fundamentals of Urban Development: In general, the concept of density in the urban planning literature in the context of land use planning under the category of zoning regulations is the matter dealt with the spatial distribution of elements, functions and activities in urban areas. (Flame, Urban Management Quarterly, 2008, p. 36). Concentration in urban design also has a large effect on all three aspects of the artefact environment: its function, its form and its meaning. This effect is achieved through the level of user activity in the functional dimension and methods for controlling the volume, height and spacing of buildings, in the form dimension through the performance dimensions and in the semantic dimension and artifactual environment. : Building height as one of the contiguous variables on FAR is one of the most important factors in organizing the urban landscape. This criterion, proportional to the number of floors of the building, constitutes a more precise control tool that should be designed with regard to adjacent buildings and street characteristics. The impact of the building's height on creating a sense of enclosed space is significant. The sensation of being enclosed in space is essentially based on the relationship between the distance of the eyes and the height of the spatial body that encloses it. Mass and volume of the building: this is one of the other criteria that control the FAR, which plays an important role in the urban form and display. This criterion focuses on controlling the volume and distribution of the superstructure on the ground surface. Scale: is one of the other density-dependent variables, which is a complex, multifaceted and relative measure. Therefore it can be a combination of the main criteria such as mass and volume, height, slope, etc. This makes the effects of building density on physical size more pronounced. The disturbance of physical spaces, urban form and landscape is one of the negative consequences of increasing building density. Floor Area Ratio (FAR) This is the ratio of the total infrastructure construction of a chunk to the total area of ​​that chunk. (Zo Eshtyagh, 1998.4) The building density index is shown in.