0.0001
m²/s
100
cSt
100
mm²/s
0.0001
m²/s
100
cSt
100
mm²/s
The Stokes to Square Meters per Second Converter converts kinematic viscosity from the CGS unit (stokes) to the SI unit (m²/s) and the widely-used centistokes (cSt). The conversion is: 1 stokes = 10⁻⁴ m²/s = 100 centistokes = 100 mm²/s.
The stokes (St) is the CGS unit of kinematic viscosity, named after the Irish mathematician and physicist Sir George Gabriel Stokes, famous for the Stokes equations in fluid dynamics and Stokes' law for the drag force on a sphere. One stokes equals 1 cm²/s. The sub-unit centistokes (cSt) is much more practical: water at 20°C ≈ 1.004 cSt, and most lubricating oils fall in the range of 2-1000 cSt.
Kinematic viscosity is the ratio of dynamic viscosity to density: nu = mu / rho. It governs how quickly a fluid flows under the influence of gravity, which is why kinematic viscosity (rather than dynamic viscosity) determines flow behavior in gravity-driven systems, capillary tubes, and the ASTM D445 standard test method for petroleum products.
In SI engineering calculations — especially for the Reynolds number (Re = vL/nu), Grashof number, and Prandtl number — kinematic viscosity must be in m²/s. Our converter bridges the gap between CGS laboratory data (in stokes or centistokes) and SI computational requirements.
The formulas: m²/s = stokes × 10⁻⁴ (since 1 cm² = 10⁻⁴ m²), cSt = stokes × 100 (centi = 1/100). Note that 1 cSt = 1 mm²/s exactly, so these outputs are always identical.
Water at 20°C: 0.01004 St = 1.004 cSt = 1.004×10⁻⁶ m²/s. Motor oil at 40°C: ~0.32-1.0 St = 32-100 cSt. Air at 20°C: 0.151 St = 15.1 cSt = 1.51×10⁻⁵ m²/s.
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1 St = 10⁻⁴ m²/s = 100 cSt
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ISO VG 46 oil at 40°C
Multiply by 10⁻⁴ (or divide by 10,000). 1 stokes = 1 cm²/s = 0.0001 m²/s.
Multiply by 100. 1 stokes = 100 centistokes. Example: 0.5 St = 50 cSt.
Yes, exactly. 1 cSt = 1 mm²/s = 10⁻⁶ m²/s. These are completely interchangeable.
Sir George Gabriel Stokes (1819-1903) was an Irish mathematical physicist who contributed the Navier-Stokes equations, Stokes' law (sphere drag), Stokes' theorem, and fluorescence theory.
Kinematic viscosity = dynamic viscosity / density. Pa·s / (kg/m³) = (kg/(m·s)) / (kg/m³) = m²/s. The area/time dimension arises naturally from the physics.
ASTM D445 is the standard test for kinematic viscosity: a calibrated capillary tube, timed fluid flow, at a controlled temperature (usually 40°C or 100°C). Results are in mm²/s (= cSt).
ISO VG grades = kinematic viscosity in cSt at 40°C. VG 32 = 0.32 St, VG 46 = 0.46 St, VG 68 = 0.68 St, VG 100 = 1.0 St.
Air's dynamic viscosity (0.018 mPa·s) is much lower than water (1.0 mPa·s). But air's density (1.2 kg/m³) is ~830 times less than water's (998 kg/m³). Since ν = μ/ρ, the density effect dominates: ν_air ≈ 15 cSt vs ν_water ≈ 1 cSt.
Re = v × L / ν. Convert stokes to m²/s first (×10⁻⁴), then use velocity in m/s and length in m. Example: 1 m/s flow over 0.1 m plate in water: Re = 1 × 0.1 / 1.004×10⁻⁶ ≈ 99,600.
Not directly — stokes (kinematic) and poise (dynamic) measure different things. To convert: poise = stokes × density (in g/cm³). You need to know the fluid's density.
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