Gauge and Absolute Pressure
Enter your known values, leave one input blank, and solves for the missing one. Try different units for next level excitement!
Learning zone
A tire gauge reads zero in open air, yet a barometer says 101 kPa — both are right, because gauges measure pressure relative to the atmosphere while physics formulas (the gas laws especially) demand pressure relative to vacuum. A tire inflated to 220 kPa gauge actually holds 321 kPa absolute. Forgetting the conversion is the classic gas-law error, and it matters in reverse too: "vacuum" ratings like −80 kPa gauge are just 21 kPa absolute.
Gauge and Absolute Pressure
Where
- = Absolute pressure
- = Gauge pressure
- = Atmospheric pressure
Missing one of these? Work it out first, then come back
- Absolute pressure — Expansion Tank Acceptance Volume, Dynamic Pressure (q = ½ρv²)
- Gauge pressure — Hydrostatic Pressure (P = ρgh), Hydronic Static Fill Pressure
- Atmospheric pressure — Dynamic Pressure (q = ½ρv²), Pressure Head (h = P/ρg)