Diffusion Coefficient Units
The SI unit of diffusion coefficient (diffusivity) is square meter per second (m²/s), with cm²/s also common in lab and older literature.
Scope & Verification
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Explanation
The diffusion coefficient (diffusivity) has units of area per time (L²/T). In SI form, that means square meter per second (m²/s). In experimental and older literature, square centimeter per second (cm²/s) is also common, especially in diffusion tables and transport-property references.
This hub is built for both questions behind the topic: what the unit of diffusion coefficient is, and how to convert between common diffusivity units. Every route is anchored to m²/s so m²/s, cm²/s, mm²/s, and µm²/s remain exact, reversible, and purely multiplicative.
Frequently Asked Questions
What is diffusion coefficient (diffusivity)?
The diffusion coefficient quantifies how quickly species spread by molecular diffusion and has dimensions of area per time (L²/T).
What is the unit of diffusion coefficient?
The SI unit of diffusion coefficient is square meter per second (m²/s). Square centimeter per second (cm²/s) is also common in lab and older literature.
What are the common diffusion coefficient units?
Common diffusion coefficient units include m²/s, cm²/s, mm²/s, and µm²/s. m²/s is the SI unit, while cm²/s is still common in many lab references.
Why is cm²/s common in diffusion tables?
Many experimental and older references report diffusivity in cm²/s, so it remains widely used in lab tables and transport-property literature.
Why are diffusion coefficient values often very small?
Molecular diffusion in liquids, membranes, and many solids is often slow, so diffusivity values are frequently written as very small magnitudes such as 1e-9 m²/s.
Are diffusion coefficient conversions purely multiplicative?
Yes. All conversions in this hub are fixed multiplicative scale changes between area-per-time units with no offsets.