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Gas Compressibility Factor and Missing State Values

Calculate positive compressibility factor from measured gas-state quantities, or recover a supported missing quantity with a known positive factor.

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Calculator inputs

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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.

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

Formula and method

With 1 mol at 300 K in 1 m³ and absolute pressure 0.02494338785445972 bar, the default exact SI gas constant gives Z=1.

Z = PV/(nRT); PV = ZnRT

Worked example

Enter these known values and leave the other values blank.

Pressure (P)
0.02494338785445972 bar
Temperature (T)
300 K
Number of moles (n)
1 mol
Volume (V)
1 m³
Compressibility factor (Z)
1

Assumptions and limitations

  • Pressure is absolute, temperature is converted to Kelvin, and pressure, volume, molar amount, gas constant and Z must all be positive. This is a finite single-state algebraic relationship.
  • The initial molar constant is locked at the exact SI 8.31446261815324 J/(mol·K). The control remains editable for a custom positive value and can be unlocked to infer it from the other five quantities. Its SI unit is fixed even when pressure or volume units change. Display rounding does not replace the underlying exact default.
  • Z is the measured ratio PV/(nRT). Z=1 corresponds to this ideal-gas relationship; Z below or above 1 indicates departure from it. The calculation does not look up Z for a named gas or predict Z from pressure and temperature alone.
  • Provide five independent known quantities including the locked R default to recover the sixth. Clear an unknown before solving; enter all dimensional measurements with compatible units. R here is per mole, not a gas-specific constant per unit mass.

Common questions

Does this find Z for a selected substance?

No. It calculates the ratio from supplied pressure, volume, amount, temperature and R. A gas-specific property model or measured dataset is needed to predict Z from temperature and pressure alone.

Can I use a custom gas constant?

Yes. Replace the fixed-SI R control with a positive molar constant in J/(mol·K), or unlock and clear it to infer R from five other known quantities. A mass-specific constant per kilogram does not fit these molar inputs.

Why does Z=1 matter?

It means the supplied state satisfies PV=nRT using the selected molar constant. It does not prove that every state of the gas behaves ideally.

References

Use the exact SI molar gas constant 8.31446261815324 J/(mol·K) as the initial known value, replacing the rounded 8.314 default while retaining editable custom values and the unlock control. Pounds-force per square inch use the exact international pound and inch with standard gravity, replacing the rounded captured factor.

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