Chemistry

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Diffusion Coefficient Calculator.

Calculate a spherical particle's diffusion coefficient using Stokes-Einstein in SI units.

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Diffusion coefficient: 0 m²/s

Diffusion coefficient

0.000000m²/s

Educational chemistry arithmetic only. Keep units consistent and verify assumptions against your laboratory or course specification.

Use Cases

Estimate diffusion in liquids

Researchers and engineers can estimate how quickly spherical particles, such as proteins or nanoparticles, diffuse in a solvent at a given temperature and viscosity.

Example: Estimate the diffusion coefficient of a 1 nm radius particle in water at 298 K.

Validate experimental measurements

Compare theoretical diffusion coefficients with experimental data from dynamic light scattering or other techniques to check consistency.

Example: Compare calculated D with measured D for a known particle size.

Frequently Asked Questions

What is the Stokes-Einstein equation used for?
The Stokes-Einstein equation relates the diffusion coefficient of a spherical particle to the absolute temperature, dynamic viscosity of the solvent, and particle radius. It is commonly used to estimate how fast particles move in a fluid due to Brownian motion.
What units are required for this calculator?
This calculator requires SI units: absolute temperature in Kelvin (K), dynamic viscosity in Pascal-seconds (Pa·s), and particle radius in meters (m). The resulting diffusion coefficient is in square meters per second (m²/s).
Can this calculator be used for non-spherical particles?
No, the Stokes-Einstein equation assumes a spherical particle. For non-spherical shapes, the diffusion coefficient may differ, and more complex models are needed.

Tips & Common Mistakes

Tips

  • Ensure temperature is in Kelvin, not Celsius. Add 273.15 to convert from Celsius to Kelvin.
  • Use dynamic viscosity in Pa·s. If you have values in centipoise (cP), divide by 1000 to convert to Pa·s.
  • Particle radius must be in meters. Convert from nanometers (nm) by multiplying by 1e-9.
  • For accurate results, use the viscosity of the solvent at the exact temperature of interest.

Common Mistakes to Avoid

  • Forgetting to convert temperature to Kelvin, leading to incorrect diffusion coefficients.
  • Using kinematic viscosity instead of dynamic viscosity. This calculator requires dynamic viscosity in Pa·s.
  • Entering particle diameter instead of radius. The radius is half the diameter.

Last updated: August 13, 2026