Absolute / Gauge / Differential Pressure Converter (with Steps)
Use this tool to convert absolut pres (Pabs) og manometertryk (Pg) using atmospheric pressure (Patm), and to calculate Differentialtryk (ΔP) between two points. It shows the full calculation process so engineers can verify the method, document results, and copy the output into reports.
Absolute ⇄ Gauge (requires atmospheric pressure)
Differential Pressure (P1 − P2)
What’s the Difference Between Absolute, Gauge, and Differential Pressure?
Absolut tryk (Pabs) is referenced to a perfect vacuum (0 Pa absolute). It is the value you typically need for gas laws,
altitude/barometric calculations, and many vacuum applications.
Manometertryk (Pg) is referenced to local atmospheric pressure (Patm). Most industrial pressure gauges and many process sensors
report gauge pressure because it directly indicates pressure above ambient.
Differenstryk (ΔP) is the difference between two pressures (P1 and P2), widely used for filters, flow across an orifice/venturi,
HVAC airflow, and level measurement in tanks.
Most common relationship used in engineering: Pabs = Pg + Patm. If you know any two of these values, you can solve the third.
Quick Pressure Conversion Table (Common Reference Points)
These quick conversions help you sanity-check results. Values below use standard relationships and typical constants (e.g., 1 atm = 101.325 kPa, 1 bar = 100 kPa, 1 psi = 6.894757 kPa).
| Common value | KPA | bar | psi | Pa | atm |
|---|
Tip: If you work in vacuum ranges, consider using absolute pressure units and convert to gauge only when required for a specific instrument or spec sheet.
FAQ: Absolute vs Gauge vs Differential Pressure
1) How do I convert gauge pressure to absolute pressure?
Add atmospheric pressure to gauge pressure: Pabs = Pg + Patm. For example, if Pg = 200 kPa and Patm = 101.325 kPa, then Pabs = 301.325 kPa.
2) How do I convert absolute pressure to gauge pressure?
Subtract atmospheric pressure from absolute pressure: Pg = Pabs − Patm. This tells you pressure above ambient.
3) Why does atmospheric pressure matter in these conversions?
Gauge pressure is defined relative to the surrounding atmosphere. If you change altitude or local weather, Patm changes slightly, which changes the gauge/absolute relationship.
4) Is differential pressure the same as gauge pressure?
No. Gauge pressure is referenced to atmosphere at one point, while differential pressure compares two points: ΔP = P1 − P2. Differential pressure is commonly used across filters, coils, and flow elements.
5) Can I calculate ΔP using gauge pressures?
Yes—if both readings are taken with the same reference (both gauge or both absolute). When both are gauge, the atmospheric reference cancels out in the difference.
6) What is a typical atmospheric pressure value to use?
Standard sea-level atmospheric pressure is 101.325 kPa (1 atm). For higher accuracy, use a local barometer value, especially in altitude-sensitive measurements.