PSI to Inches of Water Converter

PSI, or pounds per square inch, expresses pressure as one pound-force applied across one square inch. It is widely used for tires, pumps, compressed-air systems, hydraulic equipment, and general industrial instrumentation in the United States. An inch of water column expresses the pressure exerted by a one-inch-high column of water under defined reference conditions. It is a much smaller unit, making it convenient for low differential pressures that would appear as tiny decimal PSI values. This converter uses 1 PSI equal to 27.6799048425 inches of water. To convert PSI to inches of water, multiply by that factor. To convert inches of water to PSI, divide by the same factor. For example, 0.5 PSI equals approximately 13.839952 inches of water, while 55.359809685 inches of water equals 2 PSI. The bidirectional selector lets you use either measurement as the starting value. Water-column pressure appears under several labels, including inH2O, inWC, inches WC, and inches of water gauge. These labels generally describe the same type of pressure unit, but highly precise work must identify the reference temperature and local gravity convention behind a published value. Water density changes slightly with temperature, so reference standards can yield small differences in the last digits. This calculator uses a common engineering conversion suitable for routine work. HVAC technicians frequently use inches of water to measure duct static pressure, filter pressure drop, and fan performance. Low-pressure gas systems, clean rooms, laboratories, and industrial ventilation systems also use the unit because manometers and differential sensors can display practical-sized numbers. PSI is often more convenient when comparing those readings with broader equipment ratings or specifications. A unit conversion does not determine whether a pressure is gauge, absolute, or differential. Both units can express any of those pressure types, so preserve the original reference when converting. A differential reading remains differential after conversion, and gauge pressure does not become absolute pressure merely because its unit changes. Confirm instrument calibration and reference conditions for commissioning, compliance, or safety-critical decisions. The converter provides a fast numerical translation while leaving the physical meaning of the source measurement unchanged.