This online atlas measures projects using dwelling units per acre, population per acre, and floor area ratio (FAR), the three most commonly used measurements of density. Projects are grouped into "neighborhood" scales and "block" scales, for proper comparison. Comparing projects within a defined scale is important because the larger the land mass, the more non-residential space will exist in a given area - retail, parks, services, etc., automatically lowering the dwelling units, population and FAR, and total density of an area. Density will almost always be "higher" at the "block" scale, so it is important to make comparisons within their assigned scales.
The Density Atlas was developed by a team of MIT faculty, students, and affiliated planners, architects and designers. The concept of combining the three commonly used measures of density to better understand and compare city blocks and neighborhoods emerged from a series of urban design classes which looked at housing development projects in both the United States and China.