Redlich–Kwong EOS Pressure Calculator

Advanced options estimate parameters or accept custom constants. Pressure and compressibility outputs appear after submission. Download PDF or CSV for reports and sharing fast.

Calculator Inputs

Choose how you want to provide EOS parameters.
Converted internally to Kelvin.
Ensure Vm is greater than b.
K
Used to estimate a and b.
Converted internally to Pa.
Units: Pa·m⁶·K0.5/mol².
m³/mol
Units: m³/mol.
Displayed pressure and CSV value use this unit.
Allowed range: 0 to 12.
Reset

Example Data Table

Fluid T (K) Vm (m³/mol) Tc (K) Pc (MPa) Pressure (kPa) Z
Methane 300 0.0246 190.56 4.5992 ≈ 101.21 ≈ 1.00
Carbon dioxide 320 0.0080 304.13 7.3773 ≈ 318.0 ≈ 0.96
Nitrogen 280 0.0240 126.19 3.3958 ≈ 96.8 ≈ 1.00
Example outputs are approximate and depend on rounding.

Formula Used

The Redlich–Kwong equation of state estimates real-gas pressure using temperature and molar volume:

P = RT/(Vm − b) − a / ( √T · Vm · (Vm + b) )

When critical properties are available, the parameters are estimated as:

a = 0.42748 · R² · Tc^2.5 / Pc   |   b = 0.08664 · R · Tc / Pc

R is the gas constant, Tc is critical temperature, and Pc is critical pressure.

How to Use This Calculator

  1. Select the parameter method: use critical properties or enter a and b directly.
  2. Enter temperature and choose its unit; the tool converts it to Kelvin.
  3. Enter molar volume with units; ensure Vm is larger than b.
  4. If using critical properties, provide Tc and Pc with a consistent unit.
  5. Pick your output pressure unit and preferred decimal places.
  6. Press Submit to display results above the form immediately.
  7. Use the download buttons to export the last computed report.

Tip: Keep all inputs physically meaningful to avoid singularities.

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Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.