Calculator
required fields
Formula used
Newton’s law of viscosity
μ = τ / (du/dy)
τ is shear stress (Pa). du/dy is the velocity gradient (s⁻¹). μ is dynamic viscosity (Pa·s).
Poiseuille (laminar pipe flow)
μ = (π r⁴ ΔP) / (8 Q L)
Assumes steady, incompressible, Newtonian, laminar, fully developed flow in a circular tube.
Stokes (falling sphere)
μ = (2 r² (ρs − ρf) g) / (9 v)
Valid at low Reynolds number. The calculator reports Re as a quick check.
Kinematic relation
ν = μ / ρ
ν is kinematic viscosity (m²/s). ρ is density (kg/m³). This is useful for fluids tables.
Common conversions: 1 Pa·s = 1000 mPa·s = 1000 cP = 10 P. ·
1 cSt = 1×10⁻⁶ m²/s.
How to use this calculator
- Select the method that matches your measurement setup.
- Enter the required inputs and choose their units.
- Press Submit to compute viscosity immediately.
- Review dynamic μ and, when available, kinematic ν.
- Export results using the CSV or PDF buttons.
Tip: Viscosity changes strongly with temperature; record the test temperature with your data.
Example data table (approximate)
| Fluid | Temperature | Dynamic μ | Kinematic ν (if ρ known) | Notes |
|---|---|---|---|---|
| Water | 20 °C | ≈ 1.0 mPa·s (1.0 cP) | ≈ 1.0 cSt | Reference point for many labs |
| Air | 20 °C | ≈ 0.018 mPa·s | — | Gas viscosity is much lower |
| Olive oil | 20 °C | ≈ 0.08 Pa·s (80 mPa·s) | — | Varies with composition |
| Glycerin | 20 °C | ≈ 1.5 Pa·s | — | Strongly temperature dependent |
Values are typical and can differ by purity, pressure, and temperature.