How Do I Calculate Room Differential Pressure?

Written by william hirsch
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How Do I Calculate Room Differential Pressure?
Determine differential pressure by measuring the distance between the locations of interest. (tape measure ruler image by MichMac from

Differential pressure, more commonly known as the pressure difference between two locations, depends on the vertical distance between the places, the density or compactness of the air in your room and on how rapidly gravity causes freely falling object to accelerate. This means locations at the same height in a gas have the same pressure. Air pressure physically represents the amount of force the air applies to a given area of its surroundings, and is measured by scientists and engineers in pascals. As a reference standard, air pressure at room temperature on Earth's surface is about 101,325 pascals.

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Things you need

  • Tape measure
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  1. 1

    Measure the vertical distance in inches between the two heights for which you desire the differential pressure. For example, say you get a vertical distance of 95 inches.

  2. 2

    Change the vertical distance to meters by dividing by 39.37, because there are 39.37 inches in a meter. Quantities used in scientific equations are generally measured in metric units. Performing this operation leads to 95 inches divided by 39.97 inches per meter, or 2.41 meters.

  3. 3

    Multiply the vertical height difference by the standard density of air and the acceleration due to gravity to obtain the differential pressure in pascals. Take the density of air to be 998 kilograms per cubic meter, and the acceleration due to gravity to be 9.8 meters per second squared. Completing the computation leads to 2.41 meters times 998 kilograms per cubic meter times 9.8 meters per second squared, or 23,571 kilograms per meter per square second. This answer is equivalent to 23,571 pascals, since a pascal is the same as a kilogram per meter per square second.

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