# Manometer Calculator

URL: https://speedycalculator.com/calculators/physics/manometer/
Last updated: 2026-10-30

> The manometer calculator finds the gauge and absolute pressure measured by an open U-tube manometer from the height difference of the liquid columns and the manometer liquid density.

## Inputs

- Manometer liquid
- Liquid density (kg/m³, g/cm³, g/mL, lb/ft³, lb/in³)
- Height difference h (mm, cm, m, in, µm)
- Atmospheric pressure (kPa, Pa, bar, psi, atm, MPa)
- Gravitational acceleration g (m/s², ft/s², g, cm/s²)

## Results

- Gauge pressure
- Absolute pressure

## Formula

```
p_gauge = ρ·g·h,  p_abs = p_atm + ρ·g·h
```

## Explanation

A U-tube manometer is the simplest pressure gauge: a liquid in a bent tube rises on one side in proportion to the pressure difference. Mercury manometers gave us the "mmHg" still used for blood pressure.

### How to use the Manometer Calculator

- **Manometer liquid**
- **Liquid density**
- **Height difference h**
- **Atmospheric pressure**
- **Gravitational acceleration g**

Results update as you type, every field has its own unit menu, and everything is calculated in your browser.

### How it works

Choose the manometer liquid, enter the height difference (negative for vacuum) and the atmospheric pressure.

### Inputs explained

FieldWhat to enterManometer liquidChoose one: Mercury, Water, Red gauge oil (SG 0.827), Ethanol …Liquid densityUnits: kg/m³, g/cm³, g/mL, lb/ft³, lb/in³Height difference hUnits: mm, cm, m, in, µmAtmospheric pressureUnits: kPa, Pa, bar, psi, atm, MPaGravitational acceleration gUnits: m/s², ft/s², g, cm/s²

### Example values

How the main result changes when **Liquid density** changes and everything else stays at the example values above:

Liquid density (kg/m³)Gauge pressure (kPa)50015.926875015.92681,00015.92681,25015.92681,50015.92682,00015.9268

## Worked example

Inputs — Manometer liquid: Mercury; Height difference h: 120 mm; Atmospheric pressure: 101.325 kPa; Gravitational acceleration g: 9.80665 m/s².

Results — **Gauge pressure = 15.92678 kPa**; Absolute pressure = 117.25178 kPa.

## Key terms

- **Gauge pressure**: Pressure relative to atmospheric.

## FAQ

**Why use mercury?**
Its high density keeps the column short.

**What does a negative height mean?**
The pressure is below atmospheric (vacuum).

**What is 1 mmHg?**
133.32 Pa.

**Are manometers still used?**
Yes – for calibration and low-pressure HVAC measurements.


## Sources

- [OpenStax – University Physics Volume 1](https://openstax.org/details/books/university-physics-volume-1)
- [The Engineering ToolBox](https://www.engineeringtoolbox.com/)