➔ Calculate Terminal Velocity (Fall Velocity or Settling Velocity)
➔ Calculate Acceleration Of Gravity
➔ Calculate Diameter Of a Particle
➔ Calculate Density Of Medium
➔ Calculate Density Of Particle
➔ Calculate Viscosity Of Medium
Stokes Law Calculators
Stokes' Law is used to describe the motion of a spherical particle in a viscous fluid. It is commonly applied to calculate the terminal velocity of a particle settling under the influence of gravity.
The formula for Stokes' Law is:

Where:
- vt = terminal velocity (m/s)
- r= radius of the particle (m)
- ρp = density of the particle (kg/m³)
- ρm = density of the medium (kg/m³)
- g= acceleration due to gravity (m/s²)
- η= viscosity of the medium (Pa·s)
Now let's break down the calculators you requested:
1. Calculate Terminal Velocity (Fall Velocity or Settling Velocity):
To calculate terminal velocity, use the formula above. You need the radius of the particle, densities of the particle and the medium, acceleration due to gravity, and viscosity of the medium.

2. Calculate Acceleration of Gravity (g):
If you have the other values, you can rearrange the formula to solve for gg
:
Where:
- gis the acceleration due to gravity (m/s²).
- vt is the terminal velocity (m/s).
- r is the radius of the particle (m).
- ρp is the density of the particle (kg/m³).
- ρm is the density of the medium (kg/m³).
- η is the viscosity of the medium (Pa·s).
3. Calculate Diameter of a Particle (d):
Since the radius rr
is half the diameter, rearrange the formula for r:
Then multiply r by 2 to get the diameter:

4. Calculate Density of Medium (ρm):
Rearrange the formula to solve for ρm
:
Where:
- ρm is the density of the medium (kg/m³).
- vtis the terminal velocity (m/s).
- r is the radius of the particle (m).
- ρp is the density of the particle (kg/m³).
- g is the acceleration due to gravity (m/s²).
- η the viscosity of the medium (Pa·s).
5. Calculate Density of Particle (ρp
):Rearrange the formula for ρp
:
Where:
- ρp is the density of the particle (kg/m³).
- ρm is the density of the medium (kg/m³).
- vt is the terminal velocity (m/s).
- r is the radius of the particle (m).
- g is the acceleration due to gravity (m/s²).
- η is the viscosity of the medium (Pa·s).
6. Calculate Viscosity of Medium (η):
Rearrange the formula to solve for viscosity:

Where:
- η is the viscosity of the medium (Pa·s).
- r is the radius of the particle (m).
- ρp is the density of the particle (kg/m³).
- ρm is the density of the medium (kg/m³).
- g is the acceleration due to gravity (m/s²).
- v is the terminal velocity (m/s).