Osmotic Pressure Calculator
Estimate osmotic pressure from concentration, temperature, and an effective particle factor.
01 Set up your calculation
- Enter molar solute concentration.
- Supply temperature and an effective van’t Hoff factor.
- Read the pressure estimate for a membrane that retains the solute.
02 The relationship
For the assumptions behind these results, read the explanation below. You can also explore Molarity and Molality.
Follow the numbers
A 0.1 mol/L nonelectrolyte solution at 298.15 K with i = 1 gives π ≈ 247,896 Pa, or about 2.479 bar.
03 Pressure that balances solvent flow
Osmotic pressure is the applied pressure difference needed to balance the solvent’s tendency to move across a suitable semipermeable membrane. The simple equation resembles the ideal gas law because both relate a particle concentration to a thermal energy scale.
The concentration entered here is the formula-unit concentration of the solute. The effective factor i accounts for dissociation or association. Do not enter an already particle-corrected osmolar concentration and then apply the same dissociation factor again.
04 Use the dilute-solution approximation deliberately
The linear relationship works best for sufficiently dilute solutions. Concentrated electrolytes, polymers, and strongly interacting mixtures can depart from this approximation and need measured osmotic data or a more detailed activity model.
The effective factor may include a chosen nonideality correction, but the calculator does not determine that factor from chemical identity. It also does not predict membrane permeability, filtration flow rate, or physiological suitability.
Questions from the notebook
Is molality interchangeable with molarity here?
No. This equation uses amount per solution volume. Convert the concentration basis before using it.
What factor should glucose use?
An ideal dilute nonelectrolyte estimate uses i = 1; real behavior depends on conditions.
Does this calculate pressure between two solutions?
Calculate each side consistently and take their difference when the same assumptions apply.
References & reading
- OpenStax, Rice University — Colligative Properties ↗
Gives the molality relationships for freezing and boiling shifts and the dilute-solution osmotic-pressure equation.
- NIST — Guide to SI conversion factors ↗
Supports physical unit conversions. Input values are converted to the formula’s base units before calculation.
Our explanations are written for ChemistryCalc. Read how we build and check our tools. These calculations are educational estimates where the underlying model requires assumptions.