Osmotic Pressure Calculator

Osmotic pressure (π) is the minimum pressure needed to prevent osmosis across a semipermeable membrane. It is calculated by π = iMRT, where i is the van't Hoff factor, M is molarity, R is the gas constant, and T is temperature in Kelvin.

The van't Hoff factor (i) represents the number of particles a solute dissociates into. For non-electrolytes (glucose): i=1. For NaCl: i=2 (Na⁺ + Cl⁻). For CaCl₂: i=3 (Ca²⁺ + 2Cl⁻). Real values may be slightly lower due to ion pairing.

Osmotic pressure is critical in: IV fluid preparation (isotonic solutions ~0.9% NaCl), kidney function, plant water uptake, dialysis, and reverse osmosis water purification.