A manometer turns a pressure difference into something you can see: the height of a liquid column. This calculator applies ΔP = ρgh so you can go from fluid and height straight to a pressure reading in the unit your project actually uses, or work backward from a target pressure to the column height that would produce it.
How the Manometer Calculator works
A manometer balances a column of liquid against a pressure difference. The heavier the fluid, the shorter the column needed to balance a given pressure — which is why mercury (density 13,534 kg/m³) is the classic choice for lab-scale pressure gauges, while water (1,000 kg/m³) or light oils are used for small HVAC and low-pressure readings where a taller, more sensitive column is useful. The calculator multiplies density, gravity, and height difference directly: ΔP = ρ × g × h, then converts the pascal result into kPa, mmHg, and psi so it matches whatever unit your gauge or spec sheet reports.
Inputs and what they mean
Fluid density (kg/m³) sets how sensitive the manometer is — use the preset chips for mercury, water, or a typical oil, or enter a custom value for another working fluid. Height difference (h) is the vertical gap between the liquid levels in the two arms of the U-tube, in meters; this is the number you'd actually read off a ruler next to the tube. Gravity defaults to standard Earth gravity, 9.81 m/s², and rarely needs adjusting unless you're working at high altitude or modeling a different environment.
Limits and edge cases
This calculator reports the differential (gauge) pressure a manometer measures, not absolute pressure — it does not add atmospheric pressure to the result. It also assumes an ideal, incompressible fluid at a steady reading; it does not model surface tension effects in very narrow tubes, temperature-driven density changes, or dynamic (oscillating) pressure readings. For very small height differences in narrow-bore tubes, capillary action can introduce a small reading error that this formula does not account for.