Convert between dynamic (Poise, Pa·s, cP) and kinematic (Stokes, cSt, mm²/s) viscosity units. Includes Saybolt conversion and common fluid reference table.
Viscosity describes a fluid's resistance to flow. Dynamic viscosity (µ) relates shear stress to strain rate and is measured in Pascal-seconds (Pa·s) or Poise (P). Kinematic viscosity (ν = µ/ρ) is the dynamic viscosity divided by density and is measured in m²/s or Stokes (St).
In practice, centipoise (cP = mPa·s) and centistokes (cSt = mm²/s) are the most commonly used units. Water at 20°C has a dynamic viscosity of exactly 1.002 cP — this is the historical reason for the centipoise unit.
This converter handles all common viscosity unit conversions: Pa·s, mPa·s, Poise, centipoise, m²/s, mm²/s, Stokes, centistokes, and Saybolt Universal Seconds (SUS). It also computes a sample Reynolds number to illustrate the flow regime implications.
Preset buttons load properties for water, honey, motor oil, air, and mercury. A reference table lists viscosities for eight common fluids, making this tool invaluable for fluid dynamics, chemical engineering, and lubrication analysis.
Viscosity unit conversions are constantly needed in fluid mechanics, chemical engineering, and lubrication. Different industries and countries use different units, making conversion essential.
This calculator eliminates errors by converting all units simultaneously and providing a reference table for quick lookups. The note above highlights common interpretation risks for this workflow. Use this guidance when comparing outputs across similar calculators. Keep this check aligned with your reporting standard.
ν = µ/ρ (kinematic from dynamic). 1 Pa·s = 10 P = 1000 mPa·s = 1000 cP. 1 m²/s = 10⁴ St = 10⁶ mm²/s = 10⁶ cSt. SUS ≈ 4.6·cSt + 25/cSt (for cSt < 50). SUS ≈ 4.6·cSt (for cSt > 50).
Result: ν = 1.004 cSt = 1.004×10⁻⁶ m²/s
Water at 20°C: ν = 1.002×10⁻³ Pa·s / 998.2 kg/m³ = 1.004×10⁻⁶ m²/s = 1.004 cSt.
Use consistent units, verify assumptions, and document conversion standards for repeatable outcomes.
Most mistakes come from mixed standards, rounding too early, or misread labels. Recheck final values before use. ## Practical Notes
Use this for repeatability, keep assumptions explicit. ## Practical Notes
Track units and conversion paths before applying the result. ## Practical Notes
Use this note as a quick practical validation checkpoint. ## Practical Notes
Keep this guidance aligned to the calculator’s expected inputs. ## Practical Notes
Use as a sanity check against edge-case outputs. ## Practical Notes
Capture likely mistakes before publishing this value. ## Practical Notes
Document expected ranges when sharing results.
Dynamic viscosity (µ) is the intrinsic resistance to shear flow. Kinematic viscosity (ν = µ/ρ) includes density effects — it describes how fast momentum diffuses. In the Navier-Stokes equations, kinematic viscosity appears naturally.
Water at 20°C has µ ≈ 1 cP and ν ≈ 1 cSt, making these convenient "human-scale" units. SI Pa·s values are very small numbers for common fluids.
Saybolt Universal Seconds (SUS) measures the time for 60 mL of fluid to flow through a calibrated orifice. It is used in petroleum industry standards, especially ASTM specifications for lubricants.
For liquids, viscosity decreases exponentially with temperature (Arrhenius-type behavior). Water's viscosity drops from 1.79 cP at 0°C to 0.28 cP at 100°C. For gases, viscosity increases with temperature.
Non-Newtonian fluids (blood, paint, ketchup) have viscosity that changes with shear rate. The viscosity values in this tool assume Newtonian behavior — constant viscosity regardless of shear rate.
Re = ρVL/µ = VL/ν. Lower viscosity (or kinematic viscosity) means higher Re for the same flow conditions, making turbulence more likely. Viscous fluids tend to stay laminar.