Air Density (ISA vs altitude)
Aerodynamics / Flow Properties
Table of Contents
About this calculator
Air Density (ISA vs altitude) helps estimate key flow properties values quickly.
Use it for quick design checks, what-if analysis, and early sizing decisions.
For final design, always validate with higher-fidelity methods and standards.
Inputs
Enter the required values used in the formula for Air Density (ISA vs altitude).
Required inputs for calculation
Default values are prefilled where applicable. You can overwrite them.
- Altitude (h) (m) - ISA altitude above mean sea level, valid from 0 to 86,000 m
Results
Results are hidden until you click Calculate.
Formula used for calculations
rho(h) = P(h) / (R * T(h))
Temperature by ISA layer
0-11 km: T = 288.15 - 0.0065h
11-20 km: T = 216.65
20-32 km: T = 216.65 + 0.001(h - 20000)
32-47 km: T = 228.65 + 0.0028(h - 32000)
47-51 km: T = 270.65
51-71 km: T = 270.65 - 0.0028(h - 51000)
71-86 km: T = 214.65 - 0.002(h - 71000)
Pressure relation used in each layer
Lapse-rate layers: P = P_b * (T / T_b)^(-g0 / (R * L))
Isothermal layers: P = P_b * exp(-g0(h - h_b) / (R * T_b))
At every boundary, compute P_b and T_b first, then carry them into the next layer.
This calculator uses the standard ISA layer model from sea level to 86 km. Base temperature and pressure are propagated across every layer boundary so the density profile stays continuous, with g0 = 9.80665 m/s^2 and R = 287.05 J/kg.K.
Assumptions
- Inputs are in consistent units.
- The selected formula is a simplified engineering relation.
- Results are intended for preliminary analysis.
Recommendations
- Validate boundary conditions before using outputs in design decisions.
- Compare multiple scenarios by varying one input at a time.
- Use conservative margins for safety-critical use cases.
FAQs
What does Air Density (ISA vs altitude) calculate?
It computes a key value in flow properties using a standard aerospace engineering formula.
Are these results suitable for certification work?
Treat this as a fast estimation tool. Use detailed models and standard references for certification.
Why are results hidden initially?
Results appear only after Calculate so inputs and outputs remain clearly separated.