The purpose of this paper is to present a new form of chart, which clarifies the inter-relationships between six fundamental urban design parameters that affect the quality and character of any urban layout. These parameters are: built-up area per capita; public ground area per capita (which includes streets and parks); plot factor (the ratio of land area given over to private development to land area available for public use, including that needed for circulation and area available for sport, recreation and public amenities (schools, hospitals, public toilets); floor space index (ratio of built-up area to buildable plot area); net density (population divided by the sum of all buildable plot areas); and gross density (population divided by total area). Mapping these six parameters in a chart shows the complicated trade-offs between one desirable feature and another, including combinations that show that higher densities do not necessarily mean small accommodation and inadequate public space – but they do mean high-rise, and there are severe limits on how high densities can go. The paper also plots diagrams that show the values of these parameters for existing localities in New York, Mumbai (including Dharavi) and Delhi. These diagrams are examples. With more data and more diagrams we might reach a better understanding of what particular values or combinations of values for these parameters we should aim for when designing a new development or modifying an old one. We might also understand the values or combinations of values that we should avoid.