Manometer Calculator — Gauge & Absolute Pressure
Calculate the gauge pressure and absolute pressure produced by a fluid column in a U-tube or well-type manometer — choose your fluid, enter the height difference, and convert to any common pressure unit.
Fluid
m
Pa
Output unit
Pressure above atmospheric — ρ × g × h
Gauge pressure: ρ × g × h
Absolute pressure: P_atm + P_gauge
Result in kPa
- 1
Gauge pressure (Pa): ρ × g × h
1,000 × 10 × 0.5 = 4,903.33ρ is fluid density (kg/m³), g = 9.80665 m/s², h is the column height difference (m). - 2
Absolute pressure (Pa): P_atm + P_gauge
101,325 + 4,903.33 = 106,228.33 - 3
Gauge pressure in kPa
4,903.33 × 0.001 = 4.9033
How does this calculator work?
Manometer gauge pressure = ρ × g × h (density × gravity × column height). Absolute pressure = P_atm + P_gauge. A 1 m water column gives ≈ 9.8 kPa; a 1 mm mercury column gives ≈ 133.3 Pa (1 Torr). Results convert to Pa, kPa, bar, psi, mmHg or atm.
Formula
How this is calculated
A manometer measures pressure by balancing an unknown pressure against the weight of a fluid column. In a U-tube manometer open to atmosphere on one side, the gauge pressure equals ρ × g × h, where ρ is the fluid density (kg/m³), g = 9.80665 m/s² is standard gravitational acceleration, and h is the vertical height difference (m) between the two fluid surfaces. This is the classic hydrostatic equation for a static, uniform fluid.
Absolute pressure adds the atmospheric pressure to the gauge: P_abs = P_atm + P_gauge. Standard atmospheric pressure is 101 325 Pa (1 atm). At sea level, 1 m of water produces approximately 9 807 Pa (≈ 9.8 kPa) of gauge pressure, while 1 mm of mercury produces approximately 133.3 Pa (1 Torr).
This calculator supports water, mercury, oil and glycerol (or a custom density) and converts results to Pa, kPa, bar, psi, mmHg/Torr or atm. It assumes the fluid is at hydrostatic rest with uniform density and that the height h is measured vertically. For inclined or multi-fluid manometers, additional trigonometry and density weighting are required.
Frequently asked questions
Gauge pressure is the pressure relative to atmospheric pressure — it is what a manometer open to the atmosphere reads directly. Absolute pressure includes atmospheric: P_abs = P_atm + P_gauge. A gauge reading of 0 Pa means the pressure equals atmospheric.
Mercury is about 13.6 times denser than water, so a mercury manometer is 13.6 times more compact for the same pressure range. This makes it practical for blood pressure and barometric measurement, which would otherwise require a 10-metre water column.
Gauge pressure P_gauge = ρ × g × h, where ρ is fluid density (kg/m³), g = 9.80665 m/s², and h is the vertical height difference of the fluid surfaces (m). Absolute pressure P_abs = P_atm + P_gauge.
TG we-Calculate Editorial Team. (2026). Manometer Calculator — Gauge & Absolute Pressure [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/manometer-calculator
TG we-Calculate Editorial Team. "Manometer Calculator — Gauge & Absolute Pressure." TG we-Calculate. 2026. https://we-calculate.com/calculator/manometer-calculator.
TG we-Calculate Editorial Team, "Manometer Calculator — Gauge & Absolute Pressure," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/manometer-calculator
@misc{wecalculate_manometer_calculator, title = {Manometer Calculator — Gauge & Absolute Pressure}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/manometer-calculator}}, year = {2026}, note = {TG we-Calculate} }
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