How to Convert Inches of Water to PSI With a Gauge

Take time to learn how to read a pressure gauge.

Inches of water, or inch water column (wc), is the unit of pressure preferred in a few unusual applications. It is used where pressure values are small and would result in fractional numbers when expressed in more commonly used units. The unit is sometimes referred to as "inches of water gauge." Inches of water is not part of the International Standard of Units (SI).

Pressure expressed in inches of water may be converted to SI units, such as psi (pounds per square inch), using simple mathematics.

Things You'll Need

• Pressure gauge reading in inches of water (wc)
• Calculator

Instructions

1. Read the pressure in inches of water from the pressure gauge. Interpolate as necessary on an analog gauge.

2. 

   Use a calculator for speed and accuracy.

   Enter the pressure reading on the calculator and divide by 0.036126. The answer is pressure in psig, or pounds per square inch gauge.

3. Convert to psia, or pounds per square inch absolute, if necessary. To do so, add atmospheric pressure (14.696 psi) to the psig value.

References

• Converting inches of water to psig, University of North Carolina
• Converting psig to psia, Clarkson College
• Units background, Wisconsin Technical College System