PSI to Inches of Water Converter
Convert PSI to inches of water (inH₂O) with this free pressure converter. Ideal for HVAC static pressure, gas manifold testing, and engineering use.
About This Calculator
This PSI to inches of water converter instantly converts pressure measurements from pounds per square inch (PSI) to inches of water (inH₂O). It is designed for HVAC technicians, engineers, plumbers, and anyone who needs to work with low-pressure measurements using water column manometers. Simply enter your PSI value and the calculator provides the precise equivalent in inches of water.
The conversion uses the standard formula: inH₂O = PSI × 27.6807. This factor is derived from the hydrostatic pressure equation P = ρgh, where ρ is the density of water at 4°C (maximum density), g is standard gravity, and h is the height of the water column. One PSI equals the pressure exerted by a column of water approximately 27.68 inches tall.
Inches of water (inH₂O) is a non-SI pressure unit widely used for measuring low pressures and pressure differentials. Common applications include HVAC static pressure measurement in ductwork, gas appliance manifold pressure testing, laboratory manometer readings, and filter pressure drop monitoring. While the US commonly uses a 60°F reference (factor 27.7076), this calculator uses the scientific standard 4°C reference for consistency.
Regional Notes
United States: PSI and inH₂O are both commonly used in US engineering and HVAC industries. Static pressure in residential and commercial duct systems is typically measured in inches of water column (often abbreviated as "WC" or "w.c."). Gas appliance manifold pressures are also specified in inches of water.
United Kingdom: While the UK primarily uses metric pressure units (Pa, kPa, bar), inches of water is still encountered in older HVAC systems and industrial applications. The conversion factor remains the same for standard conditions.
India: PSI is used in some industrial and automotive contexts, but inches of water is less common. Metric units (Pascals, bar) are preferred for most engineering applications. This converter helps bridge the gap when working with imported equipment or US specifications.
Frequently Asked Questions
How do you convert PSI to inches of water?
To convert PSI to inches of water, multiply the PSI value by 27.6807. For example, 1 PSI equals 27.6807 inH₂O at 4°C (standard water density). This conversion factor is based on the relationship between pounds per square inch and the hydrostatic pressure exerted by a column of water.
What is a PSI to inches of water converter used for?
A PSI to inches of water converter is commonly used in HVAC (heating, ventilation, and air conditioning) for measuring static and differential pressure in duct systems, in engineering for low-pressure gas flow measurements, and in industrial applications where water column manometers are used for pressure readings.
Is 27.6807 the exact conversion factor for PSI to inH₂O?
The factor 27.6807 is the standard conversion at 4°C (39.2°F) where water reaches its maximum density. At 60°F (15.6°C), commonly used in US engineering, the factor is approximately 27.7076. The difference is about 0.1%, so both values are acceptable depending on the reference temperature.
How many inches of water is 1 PSI?
1 PSI is equal to 27.6807 inches of water (inH₂O) at standard water density (4°C). This means a column of water 27.68 inches tall exerts a pressure of about 1 PSI at its base.
Can I convert inches of water back to PSI?
Yes, to convert inches of water back to PSI, divide the inH₂O value by 27.6807. For example, 27.6807 inH₂O divided by 27.6807 equals 1 PSI. The reverse formula is PSI = inH₂O / 27.6807.
What is the difference between PSI and inches of water?
PSI (pounds per square inch) is an imperial pressure unit commonly used for tire pressure, hydraulic systems, and general pressure measurements. Inches of water (inH₂O) is a non-SI unit used for measuring low-pressure differences, particularly in HVAC duct static pressure, gas appliance manifold pressure, and laboratory manometer readings.
Is this PSI to inches of water converter free to use?
Yes, all calculators on Calculy, including this PSI to inches of water converter, are completely free to use with no registration or hidden fees. You can use it as many times as you need for personal, educational, or professional purposes.