The Gauge Pressure Calculator helps you find the gauge pressure of a system by subtracting atmospheric pressure from absolute pressure. This tool is important in fluid mechanics, engineering, and HVAC systems because it tells you how much pressure is being applied above the normal atmospheric level.
This calculator falls under the pressure and fluid dynamics calculator category.
Gauge pressure is commonly used in day-to-day applications such as tire pressure measurement, water system pressure, gas cylinder filling, and industrial process monitoring. It helps technicians, engineers, and hobbyists understand how much force is being applied within a closed system, excluding the effect of surrounding air pressure.
formula
Main Formula for Gauge Pressure (Pg):
Pg = Pabs - Patm
Where:
Pg = Gauge Pressure (usually in Pascals, bar, or psi)
Pabs = Absolute Pressure (same unit as Pg)
Patm = Atmospheric Pressure (same unit as Pg)
If Absolute Pressure (Pabs) is not directly known and needs to be calculated:
Pabs = Pg + Patm
Standard Atmospheric Pressure (Patm) Values for Reference:
101325 Pa (Pascals)
1 atm
1.01325 bar
14.7 psi
Use the appropriate unit based on your application.
Reference Table for Common Pressure Conversions
This table helps you quickly convert between various pressure units without recalculating each time.
| Unit | 1 atm Equivalent | Common Use Cases |
|---|---|---|
| Pascal (Pa) | 101325 Pa | Scientific, lab environments |
| Kilopascal (kPa) | 101.325 kPa | Weather, automotive |
| Bar | 1.01325 bar | Industrial equipment, compressors |
| psi | 14.7 psi | Tire pressure, gas cylinders |
| mmHg | 760 mmHg | Medical, laboratory instruments |
| Torr | 760 Torr | Vacuum systems, physics experiments |
Use this table when converting pressure readings or selecting units for your gauge pressure calculation.
Example
Let’s go through a simple example to see how the Gauge Pressure Calculator works.
Given:
- Absolute pressure (Pabs) = 202650 Pa
- Atmospheric pressure (Patm) = 101325 Pa
Step 1: Use the formula
Pg = Pabs - Patm
Pg = 202650 - 101325 = 101325 Pa
Final Answer:
Gauge Pressure (Pg) = 101325 Pa
This means the pressure in the system is one atmosphere above the surrounding air pressure.
Most Common FAQs
Gauge pressure is the pressure measured relative to the atmospheric pressure around you. It tells you how much pressure is in a system beyond what is naturally in the air.
No, gauge pressure can be negative. This happens when the pressure inside the system is lower than the atmospheric pressure. This negative value is often called vacuum pressure.
Gauge pressure is more practical in everyday situations because it shows how much pressure is being added or removed compared to the normal atmospheric level. For example, a tire gauge reads gauge pressure to show how much air you’ve pumped in, not including air already present in the atmosphere.