Kinematic Viscosity Calculator (cP to cSt, Dynamic ↔ Kinematic)

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Updated November 5, 2026
Kinematic Viscosity Calculator (cP to cSt, Dynamic ↔ Kinematic): formula and free online calculator

Dynamic viscosity measures a fluid's resistance to shear, while kinematic viscosity is that resistance divided by density. This kinematic viscosity calculator converts between the two with ν = μ ÷ ρ — so cP becomes cSt — as covered in viscosity measurement explained.

cSt
calculated
Type in any field to change it. Press × on a value to calculate that field instead.

How to use the kinematic viscosity calculator

Enter the dynamic viscosity (pick cP, mPa·s, P or Pa·s) and the density at the same temperature. The calculator returns the kinematic viscosity in centistokes (mm²/s). To go from cSt to cP, clear the dynamic viscosity and enter the kinematic value.

Kinematic viscosity formula

ν = μ ÷ ρ  ·  ν (cSt) = μ (cP) ÷ ρ (g/cm³)

Worked example

Water at 20 °C, μ = 1.002 cP and ρ = 998.2 kg/m³:

  • ν = 0.001002 ÷ 998.2 = 1.004 × 10⁻⁶ m²/s = 1.0038 cSt

Dynamic and kinematic viscosity of common fluids

Fluid μ (cP) ρ (kg/m³) ν (cSt)
Water, 20 °C 1.002 998.2 1.004
Water, 80 °C 0.355 971.8 0.3653
Air, 20 °C 0.0181 1.204 15.03
Petrol 0.6 740 0.8108
Diesel 3 840 3.571
Ethylene glycol, 20 °C 16.1 1113 14.47
SAE 30 oil, 40 °C 90 875 102.9
Glycerine, 20 °C 1412 1260 1121

Notes

  • Viscosity changes strongly with temperature — always use μ and ρ at the same temperature.
  • 1 P (poise) = 100 cP = 0.1 Pa·s; 1 St (stokes) = 100 cSt = 10⁻⁴ m²/s.

Frequently asked questions

How do I convert cP to cSt?

Divide by the density in g/cm³ — cSt = cP ÷ SG. Water at 20 °C is 1.002 cP ÷ 0.998 = 1.004 cSt.

What is the kinematic viscosity formula?

ν = μ ÷ ρ. In SI, Pa·s ÷ kg/m³ gives m²/s; 1 cSt = 1 mm²/s = 10⁻⁶ m²/s.

Which viscosity does the Reynolds number use?

Either — Re = ρvD ÷ μ = vD ÷ ν. Use kinematic viscosity when the fluid data is given in cSt.

Why do lubricating oils use cSt?

Oil viscosity grades (ISO VG) are measured with gravity-driven capillary viscometers, which directly measure kinematic viscosity in cSt at 40 °C.

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