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ICAO Standard Atmosphere Altitude and Pressure Calculator

Calculate Altitude & Pressure Parameters
Select Answer Mode
Altitude (H) [?]
Pressure (P) [?]
Altitude 1 (H1) [?]
Altitude 2 (H2) [?]
Pressure Difference (ΔP = P2 - P1) [?]
Pressure 1 (P1) [?]
Pressure 2 (P2) [?]
Altitude Difference (ΔH = H2 - H1) [?]

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Change the answer mode for this tool by selecting altitude (H), altitiude difference (ΔH), pressure (P), or pressure difference (ΔP) as the parameter to calculate instead




Atmospheric pressure measurement products
  • 800 to 1200 mbar atmospheric pressure transmitter
  • SIL 2 certified 800 to 1200 mbar abs range air pressure transmitter
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  • DPS Low Differential Pressure Transmitter Low pressure inflatable control with atmospheric pressure changes

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Contents

  • Related Tools
  • User Guide
    • Formulas
      • Symbols
      • Atmospheric Layer Constants
    • Altitude (H)
    • Pressure (P)
    • Altitude 1 (H1)
    • Altitude 2 (H2)
    • Pressure Difference (ΔP = P2 – P1)
    • Pressure 1 (P1)
    • Pressure 2 (P2)
    • Altitude Difference (ΔH = H2 – H1)

Related Tools

  • US Standard Atmosphere Altitude and Pressure Calculator
  • Pressure unit conversion
  • Height unit conversion

User Guide

This tool which is based on the icao standard atmosphere model will calculate the air pressure at a height above or below sea level, the altitude from the atmospheric air pressure at the same level, the pressure difference between two altitudes, and the altitude difference between two atmospheric pressures.

The method and formulas used are based on the ICAO Standard Atmosphere 1993 model for use from a height of 5000 metres below mean sea level up to a height of 80,000 metres above mean sea level. The atmospheric model assumes the air is a dry ideal gas, with an atmospheric pressure of 101325 Pa and a temperature of 288.15 K at mean sea level.

In reality the atmospheric pressure, temperature & humidity level in the air are constantly changing, therefore the accuracy in determining the true altitude is limited by this. However despite the dynamic nature of the atmosphere, standard atmosphere models serve as a way of standardising measuring instruments. If every measurement instrument is calibrated with the same atmospheric model the readings can be directly compared.

Vacuum range absolute pressure measurement products
  • DS200 Combined Pressure Switch, Gauge and Sensor
  • Depression vacuum 1 bar absolute range 0-5V output automotive test pressure sensor
  • Vacuum insulation 15 psi absolute range millivolt output pressure sensor for air extraction use
  • 15 psi absolute vacuum range 0-5 volts output pressure sensor

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Formulas

The formulas used by this icao standard atmosphere altitude and air pressure calculator to determine each individual parameter are:

For βb ≠ 0:

P = Pb · (1 + (βb · (H – Hb) / Tb))-g / (βb · R)

H = ((((P / Pb) –βb · R / g – 1) / βb) * Tb) + Hb

For βb = 0

P = Pb · e-g · (H – Hb) / (R · Tb)

H = (ln(P / Pb) · R · Tb / -g) + Hb

ΔP = P2 – P1

ΔH = H2 – H1

Symbols

  • P = Atmospheric pressure at altitude H
  • ΔP = Atmospheric pressure difference from H1 to H2 altitude
  • Pb = Atmospheric pressure at interfaces between atmosphere transitional layers from b = 0 to 6
  • H = Geopotential altitude relative to mean sea level
  • ΔH = Geopotential altitude difference from  P1 to P2 atmospheric pressure
  • Hb = Geopotential altitude from mean sea level of interfaces between atmosphere transitional layers from b = 0 to 6
  • Tb = Reference temperature at interface between atmosphere transitional layers from b = 0 to 6
  • βb = Standard temperature lapse rate to change reference temperature (Tb) between atmosphere transitional layers from b = 0 to 6
  • g = Standard acceleration due to gravity = 9.90665 m/s2
  • R = Specific gas constant = 287.05287 J/K·kg, constant value defined by ICAO Standard Atmosphere 1993, and derived from ideal gas law equation; P = ρ·R*·T/M0, where P = 101,325 Pa, ρ = 1.225 kg/m3, R* = 8,314.32 J/K·kmol,  T = 288.15 K, M0 = 28.964420 kg/kmol), P/(ρ·T) = R* / M0 = R

Atmospheric Layer Constants

b Height (m) Pressure (Pa) Reference Temperature (K) Lapse Rate (K/m)
0 0 101,325 288.15 -0.0065
1 11,000 22632.0401 216.65 0
2 20,000 5474.87742 216.65 0.001
3 32,000 868.015777 228.65 0.0028
4 47,000 110.905773 270.65 0
5 51,000 66.9385281 270.65 -0.0028
6 71,000 3.95639216 214.65 -0.002

Altitude (H)

This is the geopotential height above or below mean sea level.

Pressure (P)

This is the absolute pressure of air at a particular level in the atmosphere.

Altitude 1 (H1)

This is the initial altitude used in calculating the atmospheric pressure difference between two altitudes.

Altitude 2 (H2)

This is the final altitude used in calculating the atmospheric pressure difference between two altitudes.

Pressure Difference (ΔP = P2 – P1)

This is the atmospheric pressure difference when changing altitude from H1 to H2.

Pressure 1 (P1)

This is the initial atmospheric used in calculating the altitude difference between two atmospheric pressures.

Pressure 2 (P2)

This is the final atmospheric used in calculating the altitude difference between two atmospheric pressures.

Altitude Difference (ΔH = H2 – H1)

This is the altitude difference when changing atmospheric pressure from P1 to P2.

Atmospheric pressure measurement products
  • DMP331 Precision Pressure Transmitter
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  • Barometric & Atmospheric Pressure Gauges

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Product Selection Guides

  • Data Loggers
  • Differential Pressure Sensors
  • Digital Pressure Gauges
  • Digital Pressure Sensors
  • Digital Readouts
  • Hydrostatic Liquid Level Sensors
  • Millivolt Output Pressure Transducers
  • Pressure Transducers
  • Pressure Transmitters
  • Voltage Output Pressure Transducers

Application Selection Guides

  • Absolute Pressure
  • Differential Pressure
  • Dual Temperature and Pressure
  • Flush Diaphragm
  • High Frequency Response
  • Low Pressure Range
  • Overpressure Protection
  • Vacuum

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