Gauge Pressure Calculator
Work out gauge pressure instantly with clear inputs, formula shown and shareable results.
About Gauge Pressure Calculator
Gauges read zero at atmospheric pressure, so an absolute figure needs the ambient pressure added back: 220 kPa gauge is 321 kPa absolute at sea level. This matters for gas law calculations, which always need absolute pressure - using a gauge reading there is one of the commonest errors in thermodynamics problems.
Formulas
Absolute pressure
P(absolute) = P(gauge) + P(atmospheric)
Vacuum
negative gauge pressure means below ambient
Worked example
With the default values below, Gauge Pressure Calculator returns Absolute Pressure of 321.325. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Gauge pressure reading
- 220 kPa
- Local atmospheric pressureminimum 0 kPa
- 101.325 kPa
Results
- Absolute Pressure
- 321.325 kPa
- Same Pressure In Bar
- 3.2133
- Gauge Reading In psi
- 31.908
- Interpretation
- Above atmospheric - positive gauge pressure
Step by step
- 1Values used
- 2Absolute pressure
- 3Vacuum
- 4Absolute Pressure= 321.325 kPa
- 5Same Pressure In Bar= 3.2133
- 6Gauge Reading In psi= 31.908
- 7Interpretation= Above atmospheric - positive gauge pressure
Assumptions and limits
- The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
Why do tyre pressures use gauge?
Because the tyre's structural load is the difference across the wall. The atmosphere pushes back on the outside, so only the excess matters.
Which pressure do the gas laws need?
Absolute, always. PV = nRT counts molecules, and molecules do not know where the gauge was zeroed.