Ideal gases have Z = 1. Real gases deviate at high pressures and low temperatures: attractive forces make Z < 1 and molecular size makes Z > 1. Natural gas pipelines and high-pressure tanks rely on Z for accurate quantities.
How to use the Compressibility Factor Calculator
- Pressure p
- Volume V
- Amount n (mol)
- Temperature T
Results update as you type, every field has its own unit menu, and everything is calculated in your browser.
How it works
Enter the measured pressure, volume, amount and temperature.
Tips
- Use absolute temperature (K) in gas laws and efficiency formulas.
- Temperature differences are the same in K and °C.
- Heat = mass × specific heat × temperature change when no phase change occurs.
- Phase changes need latent heat at a constant temperature.
Common mistakes to avoid
- Using °C in pV = nRT.
- Forgetting latent heat during melting or boiling.
- Confusing heat capacity (J/K) with specific heat (J/(kg·K)).
Inputs explained
| Field | What to enter |
|---|---|
| Pressure p | Units: kPa, MPa, bar, atm, psi |
| Volume V | Units: L, m³, mL, ft³ |
| Amount n (mol) | A number |
| Temperature T | Units: K, °C, °F |
What each result means
- Compressibility factor Z = [Pressure p]×[Volume V]÷([Amount n (mol)]×8.314462618×[Temperature T])
- Ideal gas volume = [Amount n (mol)]×8.314462618×[Temperature T]÷[Pressure p]
Example values
How the main result changes when Pressure p changes and everything else stays at the example values above:
| Pressure p (kPa) | Compressibility factor Z |
|---|---|
| 5,000 | 0.4009 |
| 7,500 | 0.6014 |
| 10,000 | 0.8018 |
| 12,500 | 1.0023 |
| 15,000 | 1.2027 |
| 20,000 | 1.6036 |
Formula
Z = p·V / (n·R·T)Worked example
Inputs — Pressure p: 10,000 kPa; Volume V: 0.2 L; Amount n (mol): 1; Temperature T: 300 K.
Results — Compressibility factor Z = 0.80182; Ideal gas volume = 0.24943 L; Behaviour = Attractive forces dominate (Z < 1).
Key terms
- Real gas
- A gas whose behaviour deviates from pV = nRT.
Frequently asked questions
What does Z = 1 mean?
The gas behaves ideally.
When is Z less than 1?
At moderate pressures, when attractions pull molecules together.
When is Z greater than 1?
At very high pressures, when molecular volume matters.
How is Z found in practice?
From charts of reduced pressure and temperature or equations of state.
What formula does the Compressibility Factor Calculator use?
Z = p·V / (n·R·T).