Barometric Altitude Calculator
Estimate your altitude above sea level from barometric pressure readings.
Uses the hypsometric formula for accuracy.
Barometric pressure decreases with altitude because there is less atmosphere above you as you go higher. This relationship allows us to estimate altitude from a pressure reading.
The hypsometric formula:
h = (T + 273.15) / 0.0065 × (1 − (P / P₀)^0.190284)
Where:
- h = altitude in meters
- T = temperature in °C at the measurement point
- P = observed pressure at altitude
- P₀ = sea-level reference pressure (standard: 1013.25 hPa)
Standard atmospheric pressure at sea level is defined as:
- 1013.25 hPa (hectopascals) = 1013.25 mbar (millibars)
- 29.9212 inHg (inches of mercury)
- 760 mmHg (millimeters of mercury)
- 14.696 psi (pounds per square inch)
Approximate pressure decrease with altitude:
- Sea level: 1013 hPa
- 1,000 m (3,280 ft): 899 hPa
- 2,000 m (6,562 ft): 795 hPa
- 3,000 m (9,843 ft): 701 hPa
- 5,000 m (16,404 ft): 540 hPa
- 8,849 m (29,032 ft, Mt. Everest summit): ~337 hPa
Accuracy considerations: Temperature significantly affects the result. Cold air is denser, so pressure drops faster with altitude in cold weather. Weather systems also cause pressure variations unrelated to altitude. For the most accurate reading, use the current sea-level pressure from a nearby weather station rather than the standard 1013.25 hPa.
Applications: Altimeters in aircraft, hiking GPS devices, and weather stations all use barometric pressure to estimate altitude.