Manometer Calculator

A manometer is a scientific instrument used to measure fluid pressure in gases, liquids, or pipeline systems. It typically consists of a glass tube (often U-shaped) filled with a dense liquid like mercury or water. Pressure differences cause the fluid to rise or fall, and the height difference is used to calculate the pressure.

A manometer works on the principle of hydrostatic pressure equilibrium. When pressure is applied on one side of the fluid column, it pushes the fluid down on that side and up on the other. The resulting height difference (Δh) between the two levels is proportional to the pressure difference, calculated as ΔP = ρ·g·Δh.

The fundamental manometer equation is P = ρ·g·h, where ρ is the fluid density (kg/m³), g is gravitational acceleration (m/s²), and h is the height difference of the liquid column (m). The result is pressure in Pascals (Pa). For inclined manometers, the effective vertical height is h = L·sin(θ), where L is the tube reading and θ is the inclination angle.

Mercury (ρ ≈ 13,600 kg/m³) is the most common manometer fluid because its high density allows measurement of large pressures with compact tube heights. Water (ρ ≈ 1,000 kg/m³) is used for low-pressure measurements. Oil and alcohol are also used when mercury contamination is a concern or when measuring very low pressures.

A U-tube manometer uses vertical height difference to measure pressure. An inclined manometer tilts the measurement tube at an angle, which stretches the scale and increases sensitivity for low-pressure measurements. The effective vertical height for an inclined manometer is Δh = L·sin(θ), where L is the reading along the tube and θ is the angle from horizontal.

The base SI unit is the Pascal (Pa). Common conversions are: 1 kPa = 1,000 Pa; 1 bar = 100,000 Pa; 1 psi ≈ 6,894.76 Pa; 1 atm = 101,325 Pa; 1 mmHg ≈ 133.322 Pa; 1 inH₂O ≈ 249.089 Pa. This calculator automatically converts your result into all these units simultaneously.

Manometers are widely used in HVAC systems to measure duct pressure and airflow, in laboratory settings to calibrate sensors, in process control to monitor pipeline pressure, in medical equipment (e.g., blood pressure measurement), and in aerospace to verify cabin pressure gradients. Their simple design and high accuracy make them a staple in fluid measurement.

Gravity directly determines how much force a fluid column exerts per unit height. At standard Earth gravity (9.81 m/s²), a 1-meter column of mercury exerts about 133,416 Pa. At lower gravity (e.g., on the Moon at ~1.62 m/s²), the same column would produce far less pressure. This calculator lets you adjust gravity for precision work or non-Earth environments.