What is the specific gravity of standard air?

The specific gravity of standard air is approximately 1.29 kg/m³ at sea level and at 20°C. Specific gravity is a dimensionless quantity, often expressed relative to the density of water, which has a density of about 1000 kg/m³. Therefore, the specific gravity of air can be calculated as approximately 0.00129 when compared to water. This indicates that air is much less dense than water.