Altitude Air Pressure Calculator
Calculate atmospheric air pressure at any altitude using the barometric formula.
Useful for aviation, hiking, cooking, and science.
Air Pressure
Atmospheric pressure decreases with altitude because there is less air above you pressing down. This relationship is described by the barometric formula — one of the most practically useful equations in atmospheric science.
The barometric formula (troposphere, up to ~11km):
P(h) = P₀ × (1 − L×h/T₀)^(g×M / R×L)
Where:
- P(h) = pressure at altitude h
- P₀ = sea level pressure = 101,325 Pa (1013.25 hPa)
- L = temperature lapse rate = 0.0065 K/m
- h = altitude in meters
- T₀ = sea level temperature = 288.15 K (15°C)
- g = gravitational acceleration = 9.80665 m/s²
- M = molar mass of dry air = 0.028964 kg/mol
- R = universal gas constant = 8.314 J/(mol·K)
This simplifies to approximately:
P(h) ≈ P₀ × (1 − 0.0000226 × h)^5.256
Reference pressures at key altitudes:
| Altitude | Pressure | % of sea level |
|---|---|---|
| 0m (sea level) | 1013.25 hPa | 100% |
| 1,000m (3,281ft) | 898.8 hPa | 88.7% |
| 2,000m (6,562ft) | 795.0 hPa | 78.5% |
| 3,000m (9,843ft) | 701.2 hPa | 69.2% |
| 5,500m (Everest Base Camp) | ~505 hPa | 50% |
| 8,849m (Mt. Everest summit) | ~337 hPa | 33% |
| 10,668m (cruise altitude) | ~226 hPa | 22% |
Why altitude pressure matters:
- Cooking: Water boils at lower temperatures at altitude (1°C lower per ~295m / 960ft). Recipes designed at sea level need adjustment.
- Hiking / mountaineering: Altitude sickness becomes a risk above 2,500m (8,200ft) as oxygen partial pressure decreases.
- Aviation: Aircraft cabins are pressurized to simulate conditions at ~1,800–2,400m (6,000–8,000ft) — equivalent to ~80% sea level pressure.
- Medicine: Atmospheric pressure affects dissolved gas levels in blood — relevant for diving decompression and altitude medicine.