Stokes Settling Velocity Calculator
Reviewed by Hamza Gujjar, Algorithm Architect & Software Developer
Last updated: July 27, 2026How sediments sort themselves by size
Stokes' Law describes the terminal settling velocity of small spherical particles in a viscous fluid under laminar conditions - it is the physical basis for why sediment grains sort themselves by size as they settle in water, forming the graded bedding seen in many sedimentary rock layers.
Worked example
For a 0.05mm quartz grain (density 2,650 kg/m³) settling through water (density 1,000 kg/m³, viscosity 0.001 Pa.s):
v = (2 x 0.00005² x (2650-1000) x 9.807) / (9 x 0.001) = 0.008989 m/s
Stokes' Law only applies accurately to small particles in laminar (low Reynolds number) settling conditions, roughly fine sand size and smaller - larger particles like coarse sand and gravel settle fast enough to create turbulent wakes, requiring more complex drag equations instead.