when standard temperature lapse rate equals zero. Equation 1: Equation 2: where = mass density (kg/m3) = standard temperature (K) = standard temperature lapse rate (see table below) (K/m) in ISA = height above sea level (geopotential meters) = universal gas constant 8.3144598 N·m/(mol·K) = gravitational acceleration: 9.80665 m/s2 = molar mass of Earth's air: 0.0289644 kg/mol or, converted to U.S. gravitational foot-pound-second units (no longer used in U.K.): = mass density (slug/ft3) = standard temperature (K) = standard temperature lapse rate (K/ft) = height above sea level (geopotential feet) = universal gas constant: 8.9494596×104 ft2/(s·K) = gravitational acceleration: 32.17405 ft/s2 = molar mass of Earth's air: 0.0289644 kg/mol The value of subscript b ranges from 0 to 6 in accordance with each of seven successive layers of the atmosphere shown in the table below. The reference value for ρb for b = 0 is the defined sea level value, ρ0 = 1.2250 kg/m3 or 0.0023768908 slug/ft3. Values of ρb of b = 1 through b = 6 are obtained from the application of the appropriate member of the pair equations 1 and 2 for the case when h = hb+1. In these equations, g0, M and R* are each single-valued constants, while ρ, L, T and h are multi-valued constants in accordance with the table below. The values used for M, g0 and R* are in accordance with the U.S. Standard Atmosphere, 1976, and that the value for R* in particular does not agree with standard values for this constant. {| class="wikitable" |- ! rowspan="2"|Subscript b ! colspan="2"|Height Above Sea Level (h) ! colspan="2"|Mass Density () ! rowspan="2"|Standard Temperature (T''') (K) ! colspan="2"|Temperature Lapse Rate (L) |- ! (m) !! (ft)!! (kg/m3) !! (slug/ft3) !! (K/m) !! (K/ft) |- | align="center" |0 | align="center" |0 | align="center" |0 | align="center" |1.2250 | align="center" | | align="center" |288.15 | align="center" |-0.0065 | align="center" |-0.0019812 |- | align="center" |1 | align="center" |11 000 | align="center" |36,089.24 | align="center" |0.36391 | align="center" | | align="center" |216.65 | align="center" |0.0 | align="center" |0.0 |- | align="center" |2 | align="center" |20 000 | align="center" |65,616.79 | align="center" |0.08803 | align="center" | | align="center" |216.65 | align="center" |0.001 | align="center" |0.0003048 |- | align="center" |3 | align="center" |32 000 | align="center" |104,986.87 | align="center" |0.01322 | align="center" | | align="center" |228.65 | align="center" |0.0028 | align="center" |0.00085344 |- | align="center" |4 | align="center" |47 000