Osmotic Pressure Calculator
Osmotic pressure of a solution in kilopascals, atmospheres and bar, with its osmolarity.
Results
Osmotic pressure
773.619
kPa
Pressure
7.63503
atm
Pressure
7.73619
bar
Osmolarity
300.00
mOsm/L
What this tool does
The equation has the same shape as the ideal gas law, because dissolved particles behave in much the same way. The default is physiological saline at body temperature, which comes out near 300 mOsm/L — the same figure blood plasma sits at, which is exactly why that concentration is used. Reverse osmosis has to push harder than this number to move water backwards.
Formula
Π = i × M × R × T
Variables
| Symbol | Meaning | Unit |
|---|---|---|
mo | Molarity | mol/L |
iv | van 't Hoff factor | — |
t | Temperature | °C |
PI | Osmotic pressure | kPa |
AT | Pressure | atm |
BA | Pressure | bar |
OS | Osmolarity | mOsm/L |
Worked example
- Molarity0.15 mol/L
- van 't Hoff factor2
- Temperature37 °C
- Osmotic pressure773.619 kPa
- Pressure7.63503 atm
- Pressure7.73619 bar
- Osmolarity300.00 mOsm/L
Limitations
- For work that must comply with a standard or be signed off, check the result against the applicable code and have it reviewed by a qualified engineer.
- The formula assumes ideal conditions: no friction losses, no air resistance and no efficiency losses unless you enter them.
- This tool is informational only. It does not diagnose, treat or replace a qualified health professional. Speak to a doctor before making decisions about your health.