**r = .75 (P**_{b} / 29.92) X (530 / t)

Where r = density in lb. per cubic foot

t = Rankine temperature of (°F + 460)

P_{b} = barometric pressure in inches of Hg

For sea level to 29,000 foot altitude:

**P**_{b} = 29.873 – 1.049A + .012A_{2} 3% max. error

Where A = altitude in thousands of feet

For 30,000 to 60,000 foot altitude:

**P**_{b} = 24.021 – 1.049A + .012A_{2} 3% max. error