How to Calculate Standard Barometric Pressure

How to Calculate Standard Barometric Pressure
Standard barometric pressure as reported by weather stations has been converted to an equivalent sea level reading. Knowing how to convert a local barometer reading to this equivalent is essential in determining the actual barometric pressure.

Instructions

Difficulty: Moderately Challenging

Things You’ll Need:
  • Notebook Pencil Calculator Barometer Thermometer Altimeter (or knowledge of existing altitude) Scientific conversion chart (available on the Internet)
  • Notebook
  • Pencil
  • Calculator
  • Barometer
  • Thermometer
  • Altimeter (or knowledge of existing altitude)
  • Scientific conversion chart (available on the Internet)
Step 1
The first step in calculating the local barometric pressure and converting it to sea level is to use the barometer and thermometer to calculate the local conditions. Record these conditions and also the time of calculation.
Step 2
Make sure that the degrees match the degrees on the scientific chart that you are using. Most scientific charts use the Kelvin scale which is equal to Celsius plus 273 degrees. Celsius is equal to (F -32) X 5/9 , where F equals temperature in Fahrenheit
Step 3
Calculate the pressure at sea level using a scientific scale. Be aware that temperature is also a factor, and will usually be higher at sea level. Two degrees Kelvin per 1,000 feet is a good approximation, one that is often used. Sea level is the standard for weather forecasters and this calculation will provide a basis for determining weather conditions. If the pressure at 5,000 feet is read at 24.9 Inches, it will translate to 29.92 at sea level. The scale used here is from the engineering toolbox and the website is noted below.
Step 4
Standard barometric pressure at sea level is 760 mm of mercury. This is equal to 29.92 inches of mercury or 14.7 pounds per square inch. Weather is usually good with barometric pressure readings like this. Lower pressure usually means that the weather is deteriorating. Standard barometric pressure at 5,000 feet of elevation is 24.9 inches of mercury or 12.23 pounds per square foot. At 30,000 feet, which is similar to the summit of Mount Everest, it is only 4.37 pounds per square foot.
Step 5
The temperature at which water boils can also be used to calculate atmospheric pressure. One of the websites mentioned below explains the details. There are numerous other methods that can be used to calculate barometric pressure, but most of them require scientific laboratory environments and advanced scientific knowledge.

Tips & Warnings

 
A sudden drop in atmospheric pressure usually means that the weather is deteriorating, quickly.

Article Written By John Mattson

John Mattson is an architectural engineer, adventure writer, and photographer who has traveled to many remote corners of the earth. He has recently self-published a colorfully photographed book of 26 diverse and extreme adventure stories titled "Dancing on the Edge of an Endangered Planet."

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