Manometer Calculator

A manometer determines pressure by balancing it against the hydrostatic head of a liquid column. For a stationary fluid of uniform density, the pressure difference is ΔP = ρgh, where ρ is fluid density, g is gravitational acceleration, and h is the vertical difference between liquid levels. A denser liquid or taller column represents a larger pressure difference. This calculator evaluates that relation in pascals and can convert the answer to kilopascals, bar, pounds per square inch, or millimeters of mercury. Gauge pressure is measured relative to a reference, commonly the surrounding atmosphere. The calculator labels ρgh as the pressure difference and adds it to the entered atmospheric pressure to report an absolute pressure. This addition represents the common case where the measured side is above the reference pressure. If the column indicates suction or pressure below atmosphere, the physical sign reverses and the pressure difference should be subtracted from the reference outside this nonnegative-magnitude calculator. U-tube, inclined, and differential manometers use the same hydrostatic principle. A U-tube compares liquid levels in two vertical arms. An inclined tube spreads a small vertical rise over a longer scale to improve reading sensitivity, but h in the formula must still be the vertical height, not the distance measured along the incline. A differential manometer compares two pressure points; when several fluids or connection elevations are involved, each fluid segment must be included in a complete pressure balance. The simple single-density result here applies when one manometric fluid and one effective vertical difference describe the setup. Choose density for the actual fluid and operating temperature. Water is often approximated as 1000 kg/m³, while mercury is about 13,600 kg/m³, but precise values vary with temperature and purity. Standard gravity is 9.80665 m/s², and 9.81 m/s² is adequate for many engineering estimates. Read the liquid at eye level and use the correct top or bottom of the meniscus. Avoid trapped bubbles, vibration, capillary effects, and incompatible fluids. Manometers are widely used in ventilation systems, laboratory pressure checks, flow measurements, calibration, and demonstrations because their operation is direct and traceable to length, density, and gravity.