Manometer
Calculate hydrostatic pressure using the manometer equation P = ρgh. Free online fluid pressure calculator with charts, unit conversions, and formula breakdown for students and engineers.
About This Calculator
A manometer is a scientific instrument that measures fluid pressure using the hydrostatic principle. It typically consists of a U-shaped tube filled with a high-density liquid such as mercury, water, or oil. When pressure is applied to one side of the manometer, the fluid column shifts, creating a height difference that is directly proportional to the applied pressure. This relationship is governed by the fundamental manometer equation P = ρgh, where P is the gauge pressure, ρ is the fluid density, g is gravitational acceleration, and h is the height of the fluid column.
This calculator implements the manometer equation to compute hydrostatic pressure from three key inputs: the density of the manometer fluid, the height difference of the fluid column, and the local gravitational acceleration. The density of common manometer fluids is pre-loaded — mercury (13,534 kg/m³) for high-pressure applications, water (997 kg/m³) for sensitive low-pressure measurements, and oil (920 kg/m³) for intermediate ranges. You can also enter a custom fluid density for specialized manometer fluids or different temperatures.
The calculator displays results across seven pressure units: Pascals (Pa), kilopascals (kPa), bar, pounds per square inch (psi), atmospheres (atm), millimeters of mercury (mmHg), and inches of water (inH₂O). This makes it useful for physics students studying fluid mechanics, engineers working with pressure measurements in piping systems and HVAC, and technicians calibrating pressure instruments. The breakdown section shows the complete step-by-step calculation with the formula, intermediate values, and all unit conversions.
Regional Notes
India (IN): Pressure measurements in India commonly use kPa and bar for industrial applications, while mmHg is used in medical and meteorological contexts. The standard gravitational acceleration of 9.80665 m/s² applies.
United States (US): In the US, pressure is frequently measured in psi (pounds per square inch) for engineering and automotive applications, and inH₂O (inches of water) for HVAC and low-pressure systems. mmHg is used in blood pressure measurements.
United Kingdom (UK): The UK uses a mix of metric (kPa, bar) and traditional units (psi). mmHg is used in medical contexts and atmospheric pressure reporting. This calculator supports all regional preferences.
Frequently Asked Questions
What is a manometer?
A manometer is a scientific instrument used to measure fluid pressure, typically consisting of a U-shaped tube filled with a high-density liquid such as mercury or water. It works by balancing the hydrostatic pressure of the fluid column against the unknown pressure being measured.
How does a manometer calculate pressure?
A manometer calculates pressure using the hydrostatic equation P = ρgh, where ρ is the fluid density, g is gravitational acceleration (9.80665 m/s² on Earth), and h is the height difference of the fluid column. The resulting pressure is known as gauge pressure, measured relative to atmospheric pressure.
What type of fluid is used in a manometer?
Common manometer fluids include mercury (density 13,534 kg/m³), water (997 kg/m³), oil (920 kg/m³), and ethanol (789 kg/m³). Mercury is preferred for high-pressure applications due to its high density, while water and oil are used for lower-pressure measurements where greater sensitivity is needed.
How do I use this manometer calculator?
Select your manometer fluid from the dropdown, enter the height difference in centimeters, and optionally adjust the gravitational acceleration. The calculator will instantly compute the gauge pressure and display results in multiple units including Pascals, kPa, psi, mmHg, and inches of water.
What units does this manometer calculator support?
This calculator displays pressure in Pascals (Pa), kilopascals (kPa), bar, pounds per square inch (psi), atmospheres (atm), millimeters of mercury (mmHg), and inches of water (inH₂O). The height input is in centimeters, and density is in kg/m³.
What is the difference between gauge pressure and absolute pressure?
Gauge pressure is the pressure measured relative to atmospheric pressure, which is what a simple manometer measures. Absolute pressure is gauge pressure plus atmospheric pressure (101.325 kPa at sea level). This calculator computes gauge pressure from the fluid column height.
Can this calculator be used for U-tube manometers?
Yes, this calculator supports U-tube manometers, well-type manometers, and simple barometers. The fundamental equation P = ρgh applies to all manometer types. For U-tube manometers, the height difference h represents the difference between the two fluid columns.
Is this manometer calculator free to use?
Yes, this manometer calculator is completely free to use with no registration required. You can share calculations via URL parameters by clicking Calculate — the inputs are saved in the URL for easy sharing.