Viscosity Converter

Understanding Fluid Viscosity

Viscosity measures a fluid's resistance to flow — its "thickness." Honey has high viscosity; water has low viscosity. There are two types: dynamic viscosity (μ) measures shear stress per unit velocity gradient; kinematic viscosity (ν) is dynamic viscosity divided by density.

Units and Conversions

Dynamic Viscosity (μ):

• SI unit: Pascal-second (Pa·s)
• 1 Pa·s = 10 Poise = 1,000 mPa·s = 1,000 centipoise (cP)
• Water at 20°C: μ ≈ 1.002 mPa·s = 1.002 cP

Kinematic Viscosity (ν = μ/ρ):

• SI unit: m²/s
• 1 m²/s = 10⁶ cSt (centistokes)
• Water at 20°C: ν ≈ 1.004 × 10⁻⁶ m²/s = 1.004 cSt

Viscosity of Common Fluids (at 20°C)

| Fluid | Dynamic Viscosity (mPa·s) | |-------|--------------------------| | Air | 0.018 | | Water | 1.002 | | Mercury | 1.55 | | Olive oil | 84 | | Glycerol | 1,412 | | Honey | 2,000–10,000 |

Practical Examples

Example: Oil with dynamic viscosity 50 cP, density 870 kg/m³. Kinematic viscosity = 50 × 10⁻³ / 870 = 5.75 × 10⁻⁵ m²/s = 57.5 cSt. At Re = vD/ν = 2 m/s × 0.05m / 5.75×10⁻⁵ = 1,739 → laminar flow (Re < 2,300).

Applications

Viscosity is critical for: selecting pipe sizes for oil, pump NPSH calculations, gear and bearing lubrication specification, food processing, and polymer manufacturing.