Open Space Ratio (OSR)

What is Open Space Ratio (OSR)?

Open Space Ratio (OSR) meaning The open space ratio is the amount of open space required on a residential zoning lot in non-contextual districts, expressed as a percentage of the total floor area on the zoning lot. For example, if a building with 20,000 square feet of floor area has an OSR of 20, 4,000 square feet of open space would be required on the zoning lot (0.20 × 20,000 sq ft).


reference: Glossary of Planning Terms – NYC Planning