Standard Atmosphere Calculator
At 5000 m in the International Standard Atmosphere the temperature is 255.65 K (−17.5 °C), the pressure 54.0 kPa and the density 0.736 kg/m³.
Valid from sea level to 71 km; this tool covers 0–47 km.
255.65 K
Full answer, then cut to fewer decimals (not rounded):
- 255.65 K
- 255.6 K
- Temperature
- -17.5 °C
- Pressure p
- 54019.88819 Pa
- Pressure ratio δ = p/p₀
- 0.5331348452
- Density ρ
- 0.7361155474 kg/m³
- Density ratio σ = ρ/ρ₀
- 0.600910642
- Speed of sound a
- 320.5293944 m/s
- Dynamic viscosity μ (Sutherland)
- 0.0000162811774 Pa·s
- Kinematic viscosity ν = μ/ρ
- 0.00002211769261 m²/s
Step-by-step solution
- Troposphere: T = 288.15 − 0.0065h = 255.65 K
- p = 101325 (T/288.15)^5.25588 = 54019.88819 Pa
- ρ = p ÷ (RT) = 54019.88819 ÷ (287.05287 × 255.65) = 0.7361155474 kg/m³
Standard Atmosphere Formula
T = 288.15 − 0.0065h, p = 101325 (T/288.15)^5.2559
troposphere to 11 km; isothermal 216.65 K from 11 to 20 km; ρ = p/(RT), a = √(γRT)
Worked Example
The standard atmosphere at 5000 m:
- Troposphere: T = 288.15 − 0.0065h = 255.65 K
- p = 101325 (T/288.15)^5.25588 = 54019.88819 Pa
- ρ = p ÷ (RT) = 54019.88819 ÷ (287.05287 × 255.65) = 0.7361155474 kg/m³
Pressure p: 54019.88819 Pa · Pressure ratio δ = p/p₀: 0.5331348452 · Density ρ: 0.7361155474 kg/m³ · Density ratio σ = ρ/ρ₀: 0.600910642 · Speed of sound a: 320.5293944 m/s · Dynamic viscosity μ (Sutherland): 0.0000162811774 Pa·s · Kinematic viscosity ν = μ/ρ: 0.00002211769261 m²/s
GATE tip
Density altitude questions: find ρ from the actual p and T with ρ = p/(RT), then the ISA altitude with that density. Hot days raise the density altitude and lengthen the take-off run.
More Atmosphere and Airspeed Calculators
-
Airspeed Calculator
EAS = TAS √(ρ/ρ₀), q_c = p[(1 + 0.2M²)^3.5 − 1]
CAS = a₀√(5[(q_c/p₀ + 1)^(2/7) − 1]); a₀ = 340.294 m/s, p₀ = 101325 Pa
Example: 250 knots calibrated airspeed at 10,000 ft pressure altitude: True airspeed TAS = 288.702 kn.
-
Mach Number Calculator
M = V / a, a = √(γRT)
γ = 1.4 and R = 287.05 J/(kg·K) for air; T in kelvin
Example: An aircraft at 250 m/s true airspeed at 11 km: Mach number M = 0.847258.
Frequently asked questions
What is pressure altitude?
The altitude in the standard atmosphere where the pressure equals the measured pressure. Altimeters set to 1013.25 hPa display it; flight levels are pressure altitudes in hundreds of feet.
Why does temperature stop falling at 11 km?
That is the tropopause. In the lower stratosphere (11–20 km) the standard atmosphere is isothermal at 216.65 K (−56.5 °C), then warms slowly as ozone absorbs ultraviolet light.
Sources
- The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures .
Last reviewed: . Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.
Cite this page
APA
Scientific Converters. (2026, October 15). Standard Atmosphere Calculator. Retrieved October 25, 2026, from https://scientificconverters.com/calculators/standard-atmosphere-calculator/
IEEE
Scientific Converters, "Standard Atmosphere Calculator," scientificconverters.com. Accessed: Oct. 25, 2026. [Online]. Available: https://scientificconverters.com/calculators/standard-atmosphere-calculator/