Pressão Manométrica
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
manométrica = absoluta − atmosférica
About this calculator
The gauge pressure calculator determines the difference between the absolute pressure of a system and the local atmospheric pressure. Gauge pressure, also called relative pressure, is the most common measurement in manometers and pressure sensors, as it ignores atmospheric pressure. For example, a car tire inflated to 30 psi (pounds per square inch) is measuring gauge pressure, not absolute pressure.
The calculation is straightforward: subtract atmospheric pressure from absolute pressure. Standard atmospheric pressure at sea level is 101325 Pa (or 1 atm, 14.7 psi, 760 mmHg). At higher altitudes, atmospheric pressure is lower, which affects the gauge reading. Therefore, using the correct local atmospheric pressure is important for accurate results.
This calculator is useful in various fields: engineering, mechanics, meteorology, and diving. For example, when designing piping systems, gauge pressure indicates the pressure the pipe walls must withstand above ambient pressure. In diving, the gauge pressure of an air cylinder shows how much air is available for use, disregarding the external atmospheric pressure.
Cautions: always check the pressure unit used (Pa, psi, bar, atm, mmHg). Atmospheric pressure varies with altitude and weather conditions, so for precise calculations, use the local value. Also, confirm whether the provided pressure is absolute or gauge to avoid errors. In closed systems, gauge pressure can be negative (partial vacuum), indicating pressure below atmospheric.
Frequently asked questions
What is the difference between absolute pressure and gauge pressure?
Absolute pressure is the total pressure relative to a perfect vacuum, while gauge pressure is the difference between absolute pressure and local atmospheric pressure. Gauge pressure is the typical reading on manometers.
Can I use standard atmospheric pressure (1 atm) anywhere?
No. Atmospheric pressure varies with altitude and weather conditions. For accuracy, use the local value, especially at high altitudes.
What does negative gauge pressure mean?
Negative gauge pressure indicates that absolute pressure is lower than atmospheric pressure, i.e., a partial vacuum. This is common in suction systems.
Which pressure units are supported?
The calculator supports Pa, psi, bar, atm, mmHg, and other common units. Make sure to use the same unit for both inputs.
How do I convert psi to Pa?
1 psi is approximately 6894.76 Pa. To convert, multiply the psi value by 6894.76.