Stokes Settling Velocity Calculator
Calculate the signed terminal settling or rising speed of a small sphere and check the resulting particle Reynolds number.
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Result
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Calculation steps
Work through one step at a time or reveal the complete calculation. The steps use your current inputs.
How to calculate
Convert all quantities to SI, balance buoyancy-adjusted weight against Stokes drag, preserve the density-difference sign, and verify that the calculated particle Reynolds number does not exceed 1.
v=(ρp−ρf)gd^2/(18μ); Re=ρf|v|d/μ
Worked example
A 10 μm sphere of density 2500 kg/m³ in a 1000 kg/m³ fluid of viscosity 1 mPa·s has an ideal settling speed about 0.08172 mm/s and Re about 0.000817.
Assumptions and input details
Isolated rigid smooth sphere in an unbounded Newtonian fluid at terminal speed. The result is accepted only when its calculated particle Reynolds number is at most 1. Wall, crowding, Brownian, non-spherical, turbulent, non-Newtonian and transient effects are excluded. Positive speed means settling; negative speed means buoyant rising.
References: OpenStax University Physics Volume 1: Stokes’s law
Unit definitions
Unit selection is independent of language. Each selector contains only units for its physical quantity. Calculations use defined base units internally.
Choose from 23 length definitions, including explicitly labelled regional measures. Area conversions square the length factor; geometric volumes cube it.
Regional measures are not interchangeable merely because their names look similar. This is a documented selection, not a claim to include every historical unit.
NIST measurement tables · Japanese traditional units · Mainland China and Hong Kong unit distinctions
Using this calculator
Can I enter my own problem?
Yes. Replace the example values with your own inputs. The result, calculation steps, tables and applicable diagrams update from those inputs. Blank or invalid values clear the result; example values are never silently substituted for missing inputs.
Are the results exact?
Results use floating-point arithmetic and displayed rounding. Read the formula, assumptions and any stated data precision before interpreting the result.
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The calculation runs in your browser. No account, file upload or external AI service is required. Inputs are not saved between page reloads.
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