Understanding Pressure

Published on July 31, 2025

When dealing with pressure in science, engineering, or even everyday applications like tire inflation or weather forecasting, it's essential to understand the different types of pressure measurements. The four most common types are absolute pressure, atmospheric pressure, gauge pressure, and vacuum pressure. Each plays a unique role in how we perceive and measure force in fluids or gases.

1. Absolute Pressure (Pabs)

This is the total pressure at a point, measured relative to absolute vacuum (zero pressure).

2. Atmospheric Pressure (Patm)

The pressure exerted by the Earth's atmosphere at a given location.

3. Gauge Pressure (Pgauge)

The pressure measured relative to atmospheric pressure.

4. Vacuum Pressure (Pvac)

The pressure below atmospheric pressure, essentially a negative gauge pressure.

Key Pressure Formulas

Important considerations

When a gauge pressure is positive, it indicates a pressure above atmospheric pressure.

When a gauge pressure is negative, it indicates a pressure below atmospheric pressure (a vacuum).