# Osmotic Pressure Calculator

Free osmotic pressure calculator using π = iMRT. Calculate osmotic pressure, molarity, or temperature for solutions.

## What this calculates

Calculate osmotic pressure using the van't Hoff equation: π = iMRT, where i is the van't Hoff factor, M is molarity, R is the gas constant, and T is absolute temperature.

## Inputs

- **Solve For** — options: Osmotic Pressure (π), Molarity (M), Temperature (T) — Select what to calculate.
- **van't Hoff Factor (i)** — min 1, max 10 — Number of particles the solute dissociates into. NaCl=2, CaCl₂=3, glucose=1.
- **Molarity (M)** (mol/L) — min 0 — Molar concentration of the solution.
- **Temperature** (K) — min 0 — Absolute temperature in Kelvin (K = °C + 273.15).
- **Osmotic Pressure (π)** (atm) — min 0 — Osmotic pressure in atmospheres.

## Outputs

- **Result** — The calculated value.
- **Unit** — formatted as text — Unit of the result.
- **Formula** — formatted as text — Calculation with the van't Hoff equation.

## Frequently Asked Questions

**Q: What is osmotic pressure?**

A: Osmotic pressure is the minimum pressure needed to prevent solvent from flowing through a semipermeable membrane from a dilute solution to a concentrated one. It is a colligative property that depends on solute particle concentration.

**Q: What is the van't Hoff factor?**

A: The van't Hoff factor (i) represents the number of particles a solute produces when dissolved. For non-electrolytes (glucose), i=1. For NaCl, i=2 (Na+ and Cl-). For CaCl₂, i=3 (Ca²+ and 2Cl-).

**Q: Why is R = 0.08206 used here?**

A: R = 0.08206 L·atm/(mol·K) is the gas constant in units that give pressure in atmospheres when molarity is in mol/L and temperature is in Kelvin.

**Q: What are applications of osmotic pressure?**

A: Osmotic pressure is critical in biology (cell membrane function, kidney filtration), medicine (IV solutions must be isotonic), water purification (reverse osmosis), and determining molar masses of large molecules like proteins.

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Source: https://vastcalc.com/calculators/chemistry/osmotic-pressure
Category: Chemistry
Last updated: 2026-04-21