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Diffusion Rate (Fick Law) Calculator

Work out diffusion rate (fick law) instantly with clear inputs, formula shown and shareable results.

About Diffusion Rate (Fick Law) Calculator

Applies Fick's first law: flux is proportional to the diffusion coefficient, the exchange area and the concentration gradient across the barrier.

Formula

Fick's first law

J = D x A x (dC/dx), where dC is converted from mol/L to mol/cm3 by dividing by 1000

Worked example

With the default values below, Diffusion Rate (Fick Law) Calculator returns Diffusion rate of 0.000001000. Change any input above and every figure here is recalculated in your browser.

Inputs used

Diffusion coefficientaccepts 0–1 cm2/s
0.00001 cm2/s
Cross-sectional areaaccepts 0.001–10,000 cm2
2 cm2
Concentration differenceaccepts 0–100 mol/L
0.5 mol/L
Membrane thicknessaccepts 0–10 cm
0.01 cm

Results

Diffusion rate
0.000001000 mol/s
Diffusion rate
0.003600 mol/h
Flux per unit area
0.000000500 mol/cm2/s
Concentration gradient
0.050000 mol/cm3 per cm

Step by step

  1. 1Values used
  2. 2Fick's first law
  3. 3Diffusion rate= 0.000001000 mol/s
  4. 4Diffusion rate= 0.003600 mol/h
  5. 5Flux per unit area= 0.000000500 mol/cm2/s
  6. 6Concentration gradient= 0.050000 mol/cm3 per cm

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 9 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why does thickness matter so much?

Flux is inversely proportional to distance, which is why gas exchange surfaces are only one or two cells thick.

What raises the diffusion coefficient?

Higher temperature and lower molecular size or medium viscosity all increase it.

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