Free · Unit conversions

Gauge & Absolute PSI with a Fixed Atmosphere

Convert between gauge and absolute pressure with the ambient reference explicitly fixed at one standard atmosphere.

  • Formula & worked example
  • Private in your browser
  • No signup
Go to tool

Calculator inputs

Loading calculator…

How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

Private by default

Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.

Formula and method

Zero gauge PSI corresponds to about 14.6959 absolute PSI when ambient pressure is fixed at 101,325 Pa. Ten gauge PSI corresponds to about 24.6959 absolute PSI.

Absolute pressure in Pa = gauge PSI × (0.45359237 × 9.80665 ÷ 0.0254²) + 101,325

Worked example

Enter these known values and leave the other values blank.

Pressure comparison B
0 psig (1 atm)
Pressure comparison A
14.69595 psi

Assumptions and limitations

  • The ambient reference is fixed at one standard atmosphere: 101,325 Pa. This is a modeled reference, not a measurement of local weather, elevation or a sensor reference chamber.
  • The psig option subtracts that reference. All other pressure-unit options express absolute pressure in this model, including the ordinary psi option. Read the selected unit if you change either field.
  • Negative gauge pressure is permitted above absolute vacuum. Zero absolute pressure is the lower bound; pressures below it are rejected. Enter zero in an absolute unit to calculate the exact modeled vacuum boundary.
  • PSI uses exact standard-gravity pound-force and the international inch. Optional inHg retains the approximate captured factor of 3386.39 Pa; mmHg uses 133.322387415 Pa and differs slightly from a torr.
  • For a real gauge using a different ambient reference, add that measured reference to gauge pressure in matching units. This fixed-reference tool does not substitute for that measurement.

Common questions

Why does zero gauge pressure give a positive absolute pressure?

Zero on a gauge means pressure equals the reference around the gauge. This model fixes that reference at one standard atmosphere, so zero gauge PSI is about 14.6959 absolute PSI.

Is a negative gauge reading always invalid?

No. It indicates pressure below the chosen ambient reference. It remains valid until the calculated absolute pressure reaches zero; a lower absolute value is rejected.

Can I enter the actual atmospheric pressure?

This captured model uses a fixed reference. For another ambient pressure, convert gauge pressure to the desired unit and add the measured ambient value separately.

References

Bookify rejects pressures below absolute vacuum while allowing negative gauge readings above that limit. The validation applies after converting inputs to absolute pascals. Gauge PSI uses the exact PSI factor and the captured fixed ambient offset of 101325 Pa; it does not measure local atmospheric pressure. Pounds-force per square inch use the exact international pound and inch with standard gravity, replacing the rounded captured factor. One technical atmosphere is exactly one kilogram-force per square centimeter under standard gravity. Pounds-force per square foot use the exact international pound and foot with standard gravity. The tonnes-force pressure option uses metric tonnes and standard gravity, with one tonne-force per square meter equal to 9806.65 pascals.

Explore unit conversions or browse all conversion calculators.