The Altitude Pressure Ratio Calculator calculates the atmospheric pressure at a specified altitude and expresses it as a ratio of the pressure at sea level. This functionality is crucial for predicting weather conditions, preparing for aviation operations, and conducting high-altitude scientific experiments.
Formula of Altitude Pressure Ratio Calculator
The altitude pressure ratio can be determined using the following derived formula from the barometric formula:
Pressure Ratio = (Pressure at Altitude) / (Pressure at Sea Level)
To estimate the pressure at altitude within the troposphere (up to 11 km or 36,089 feet), use:
Pressure at Altitude = Pressure at Sea Level * [1 - (Lapse Rate * Altitude) / Temperature at Sea Level] ^ (g / (R * Lapse Rate))
where:
- Lapse Rate = 0.0065 K/m, the typical rate at which temperature decreases with altitude
- Altitude = the height above sea level in meters
- Temperature at Sea Level = standard temperature at sea level, typically 288.15 K
- g = 9.80665 m/s², the acceleration due to gravity
- R = 287.05 J/(kg·K), the specific gas constant for dry air
The formula simplifies to:
Pressure Ratio = [1 - (0.0065 * Altitude) / 288.15] ^ (9.80665 / (287.05 * 0.0065))
Table for General Terms
| Term | Definition |
|---|---|
| Pressure Ratio | Ratio of the atmospheric pressure at a given altitude to that at sea level |
| Pressure at Altitude | Atmospheric pressure at the specific altitude |
| Pressure at Sea Level | Standard atmospheric pressure at sea level, typically 101325 Pascals |
| Lapse Rate | Rate of temperature decrease with increase in altitude, 0.0065 K/m |
| Altitude | Vertical distance from sea level in meters |
| Temperature at Sea Level | Standard temperature at sea level, 288.15 K |
Example of Altitude Pressure Ratio Calculator
To illustrate, if the altitude is 1,000 meters:
Pressure at Altitude = 101325 * [1 - (0.0065 * 1000) / 288.15] ^ (9.80665 / (287.05 * 0.0065))
Pressure Ratio = Pressure at Altitude / 101325
This provides a practical understanding of how atmospheric pressure changes with altitude.
Most Common FAQs
The altitude pressure ratio indicates how atmospheric pressure changes relative to sea level, which is critical for understanding environmental conditions and planning activities at various altitudes.
The accuracy depends on the precision of the input values (altitude, lapse rate, and sea level temperature). Under standard atmospheric conditions, the calculator is highly accurate for altitudes within the troposphere.
The formula provided is optimize for the troposphere (up to about 11 km). For higher altitudes, different models that account for thinner atmosphere and varying conditions are recommended.