What is the Altitude Pressure Calculator?
Convert between altitude and atmospheric pressure with this free altitude pressure calculator. Find air pressure at a given height or estimate altitude from a barometer reading using the ISA International Standard Atmosphere (troposphere to 11 km) or a barometric formula with your temperature and sea-level pressure. Results in hPa, kPa, inHg, mmHg, atm, and Pa. Results update instantly in your browser with no signup.
How to use the Altitude Pressure Calculator
- Choose Altitude → Pressure or Pressure → Altitude.
- Select ISA Standard Atmosphere or Barometric model (requires temperature and sea-level pressure).
- Pick metric (m, hPa, °C) or imperial (ft, inHg, °F) units.
- Enter altitude or pressure plus barometric inputs if needed.
- Review pressure in multiple units, ISA temperature when applicable, and calculation steps.
Common use cases
- Finding barometric pressure at a mountain summit or flight level
- Estimating pressure altitude from an altimeter or weather report
- ISA homework problems for aviation and meteorology courses
- Comparing Denver (~1600 m) or 5000 ft pressure to sea level
- Converting hPa readings to inHg or mmHg at altitude
Frequently asked questions
- What is the barometric formula?
- The barometric formula relates pressure and altitude: p = p₀ × exp(−gMh/(RT)), where p₀ is sea-level pressure, h is height, T is temperature (K), g is gravity, and M is the molar mass of air. It assumes a constant-temperature layer.
- What is the ISA standard atmosphere?
- The International Standard Atmosphere models the troposphere with a sea-level temperature of 15°C, pressure of 1013.25 hPa, and a lapse rate of 6.5°C per 1000 m. Pressure falls as p = p₀(T/T₀)^5.256 up to 11 km.
- Why does temperature matter for the barometric model?
- Warmer air is less dense, so pressure decreases more slowly with height. The barometric formula uses your entered temperature; ISA uses a fixed standard profile instead.
- What pressure is typical at 5000 feet?
- Under ISA, about 843 hPa (24.9 inHg) at 1524 m (5000 ft). Actual values vary with weather — use the barometric model with local temperature and sea-level pressure for current conditions.
- How is this related to the air density calculator?
- Both use the same barometric pressure–altitude relationship. This tool focuses on converting between altitude and pressure in many units; the air density calculator adds humidity and density from those conditions.
