An interesting website which explores settlement density in cities around the world.The Density Atlas measures case studies using a combination of population density, floor area ratio (FAR), dwelling units density, and building coverage: four commonly used density metrics. Case studies are grouped into “block”, “neighborhood”, and “district” (in increasing area) for proper comparison.
Comparing case studies at the same scale is important because the larger the land area, the more non-residential space will exist in a given area—retail, parks, services, etc.—automatically lowering the population density, FAR, dwelling unit density, and coverage. For example, density will almost always be "higher" at the "block" scale.
Check the case study areas.