You might have a number of reasons for wanting to know the atmospheric pressure, sometimes known as the barometric pressure. Atmospheric pressure is a key indicator for predicting the weather, it can have an effect on the human body and how we feel and it is an important measurement used by pilots when flying aircraft. These are the details in how to measure atmospheric pressure the easiest and most common way, by using a barometer.
Purchase or buy a barometer. You can find barometers for purchase at jewellers, clock stores, some home decor stores, garden shops or nurseries, boating or marine shops and on the Internet.
Place your barometer in a shady area that is not too susceptible to temperature changes and fluctuations. Tap the barometer lightly while you keep your eye on the indicator needle.
Note which direction the needle moves after tapping on the barometer. This will tell you whether the atmospheric pressure is rising or falling. A rising needle indicates a coming change toward better weather, a falling needle means poorer weather is coming. A needle that does not move means weather should remain steady. Note where the needle point is in reference to the numbered increments on the barometer. These will give you the actual atmospheric pressure reading in either inches or millimetres.
To convert your reading from millimetres to inches, divide the reading by 25.4.