Pressure-Based Converter
The Pressure-Based Converter turns kg into liters with the density at a set pressure. This matters most for gases.
Interactive Pressure-Based Converter Engine
Result = Value × Factor
How Pressure-Based Converter Works?
The Pressure-Based Converter works in 3 steps.
- 1
Enter the mass in kilograms (kg) of the gas or fluid.
- 2
Set the density at your pressure; for air at 15 °C (59 °F) use 0.001225 kg/L at 1 atm or about 0.242 kg/L at 200 bar.
- 3
Read the liters (L) the mass fills at that pressure.
Pressure-Based Converter Formula
The Pressure-Based Converter formula is:
Density (kg/m³) = P × M ÷ (R × T); Volume (L) = Mass (kg) ÷ Density (kg/L)P is absolute pressure in pascals (Pa), M is molar mass in kg/mol (0.02897 for air), R is 8.314 J/(mol·K) and T is temperature in kelvin (K).
Worked example
2 kg of air at 10 bar (145 psi) and 15 °C: density = 12.09 kg/m³ = 0.01209 kg/L, so volume = 2 ÷ 0.01209 = 165.4 L.
Pressure barely changes liquid density. Water compresses by about 0.005% per bar, so 100 bar (1,450 psi) raises water density by roughly 0.5%.
Pressure-Based Converter Conversion Table
The Pressure-Based Converter table gives the ideal-gas density of dry air at 15 °C (59 °F) for 10 absolute pressures from 1 bar (14.5 psi) to 300 bar (4,351 psi), with the liters that 1 kg (2.2 lb) of air fills at each pressure.
| Pressure (bar) | Pressure (psi) | Density (kg/m³) | Density (kg/L) | Volume of 1 kg (L) |
|---|---|---|---|---|
| 1 | 14.5 | 1.209 | 0.001209 | 827.14 |
| 1.01325 | 14.7 | 1.225 | 0.001225 | 816.33 |
| 2 | 29 | 2.418 | 0.002418 | 413.57 |
| 5 | 72.5 | 6.045 | 0.006045 | 165.43 |
| 10 | 145 | 12.09 | 0.01209 | 82.71 |
| 20 | 290.1 | 24.18 | 0.02418 | 41.36 |
| 50 | 725.2 | 60.449 | 0.060449 | 16.54 |
| 100 | 1,450.4 | 120.898 | 0.120898 | 8.27 |
| 200 | 2,900.8 | 241.796 | 0.241796 | 4.14 |
| 300 | 4,351.1 | 362.694 | 0.362694 | 2.76 |
Real air departs from the ideal-gas line above roughly 100 bar (1,450 psi), by up to a few percent at 300 bar.
What is Pressure-Based Converter?
The Pressure-Based Converter is a calculator that converts mass to volume with a density specified for a given pressure. Gas density rises in direct proportion to absolute pressure, so doubling pressure from 1 bar to 2 bar halves the volume of the same mass.
The tool uses the ideal gas law for the reference table. Real gases follow the ideal gas law within 1% up to roughly 50 bar (725 psi) at room temperature. Compressibility factors (Z) correct the result for higher pressures.
What are the uses of Pressure-Based Converter?
There are 4 main uses of the Pressure-Based Converter: compressed air, diving cylinders, gas cylinder filling and hydraulic systems.
Compressed air
Workshop owners estimate the free-air liters stored in a receiver tank at 8 to 10 bar.
Diving cylinders
Divers relate gas mass to volume in 200 bar and 300 bar scuba tanks.
Gas cylinder filling
Gas suppliers convert a fill mass into liters at cylinder pressure.
Hydraulic systems
Engineers check the small volume change of oil at 200 bar to 350 bar.
Pressure-Based Converter FAQ
Does pressure change the density of a liquid?
Yes, but only slightly: water density rises about 0.5% at 100 bar (1,450 psi). Gas density changes in proportion to absolute pressure.
Should I use gauge or absolute pressure?
Use absolute pressure: add 1.013 bar (14.7 psi) to a gauge reading before calculating gas density.
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