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How to Convert Torr to Altitude

The torr is a unit of pressure named after Evangelista Torricelli, the Italian physicist who discovered the principle of the barometer in 1644. There are roughly 760 torr to one atmosphere (a standard measure of atmospheric pressure -- there is roughly one atmosphere of pressure at sea level). Pressure varies from sea level to the top of the earth's atmosphere. This makes it possible to estimate pressure altitude, based on average measurements. However, pressure varies considerably based on other factors, such as weather and temperature, so this measurement is only a rough approximation. When more precision is required, it is possible to calculate the more accurate density altitude.

Things You'll Need

Pressure measurement in torr
Temperature measurement
Conversion table
Scientific calculator (optional)

Instructions

- 1
  Calculate pressure altitude by comparing the torr measurement to a standard pressure-altitude conversion table. Sea level gives approximately 760 torr, and increasing altitudes progressively lower pressures. Torr is not the standard unit for atmospheric pressure, so it may be useful to convert your torr measurement into another unit. Convert to standard atmospheres by dividing by 760, or using a conversion calculator or table.
- 2
  Calculate the more precise density altitude, if required. The formula used by the National Weather Service is as follows: DA = 145,442.16 x (1 -- ((17.326 x PA) / Tr)0.235). DA indicates density altitude (in feet). Pa indicates pressure. This is given by your torr measurement, although this equation requires a different unit: inches of mercury. Tr indicates temperature in the Rankine scale.
- 3
  Convert your torr measurement into inches of mercury (inHG). This can be done by using an online conversion calculator or table.
- 4
  Convert your temperature measurement to degrees Rankine by adding 459.67 to a Fahrenheit temperature. The conversion is slightly more difficult using degrees Celsius, so convert a Celsius score to Fahrenheit using an online converter.
- 5
  Run through the equation. First multiply your pressure measurement (in inches of mercury) by 17.326, then divide the result by your temperature measurement (in degrees Rankine). Multiply the result to the power of 0.235. Subtract the result from one. Multiply the result by 145, 442.16. The equation can be entered as it appears here into a calculator with scientific functions.

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