How to Convert Inches H2O to Mercury


The pressure of a gas can be measured by a simple device called a U-tube manometer. For low pressures, a relatively light fluid such as water can be used in the manometer. For higher pressures, a heavier liquid such as mercury may be used. Mercury is more than 13 times heavier than water, and it takes a correspondingly higher pressure to push mercury up the tube on one side of the manometer. It is quite simple to convert pressure measured in inches of water to pressure measured in inches of mercury.

Things You'll Need

  • Calculator
  • Write down the gas pressure as measured in inches of water. The ratio of the density of a substance to the density of water is called the specific gravity (SG). The SG of mercury is 13.6, meaning that mercury is 13.6 times heavier than water.

  • Take a calculator and divide the pressure measured in inches of water by 13.6. The answer is the pressure measured in inches of mercury. For example, if the gas pressure is measured at 6.8 inches of water, dividing by 13.6 equals 0.5 inches of mercury.

  • Note that gas pressure measured in mercury is more usually given in millimeters. An inch is 25.4 millimeters (mm). So a pressure of 0.5 inches of mercury is equal to 12.7 mm.

Related Searches


  • Photo Credit pressure image by Dusan Radivojevic from
Promoted By Zergnet


You May Also Like

  • What Is Specific Gravity?

    Specific gravity can be used to determine if an object will sink or float on water. The specific gravity of water is...

  • How to Convert Cm to Mm

    The metric system simplifies unit conversions, such as changing from centimeters to millimeters, by using multiples of 10. For example, snow depth...

  • How to Read a Manometer

    A manometer is a device that measures pressure with a column of liquid. A simple manometer consists of a U-shaped tube that...

  • How to Convert mm to Fractional Inches

    Converting millimeters (mm) to fractional inches is a matter of rounding to the nearest 16th of an inch, since this is how...

Related Searches

Check It Out

22 DIY Ways to Update Your Home on a Small Budget

Is DIY in your DNA? Become part of our maker community.
Submit Your Work!