Calculator Inputs
Choose a method, enter values, then press calculate. The output appears above this form and directly below the header.
Plotly Graph
The chart shows the Newtonian relationship between shear rate and shear stress using the calculated dynamic viscosity.
Example Data Table
| Method | Sample Inputs | Output Dynamic Viscosity | Equivalent cP |
|---|---|---|---|
| Shear stress ÷ shear rate | 1.8 Pa and 120 s⁻¹ | 0.015000 Pa·s | 15.000 cP |
| Parallel plate drag | 0.0075 N, 1.2 mm, 0.05 m², 1.0 cm/s | 0.018000 Pa·s | 18.000 cP |
| Laminar pipe flow | 250 Pa, 2.5 mm, 0.5 m, 0.046 L/min | 0.010072 Pa·s | 10.072 cP |
| Density × kinematic viscosity | 950 kg/m³ and 12 cSt | 0.011400 Pa·s | 11.400 cP |
Formula Used
μ = τ / γ̇
Dynamic viscosity equals shear stress divided by shear rate.
μ = (F × h) / (A × v)
Use force, fluid gap, plate area, and plate velocity for Newtonian flow between plates.
μ = (π × r⁴ × ΔP) / (8 × L × Q)
This relation comes from Poiseuille flow in a circular pipe under laminar conditions.
μ = ρ × ν
Dynamic viscosity equals density multiplied by kinematic viscosity.
Re = (ρ × V × L) / μ
This helps estimate whether the reference flow is laminar, transitional, or turbulent.
How to Use This Calculator
- Select the calculation method that matches your available data.
- Enter the measured values in the matching fields.
- Choose the correct units for every input.
- Set an optional maximum shear rate for the graph.
- Add supplementary density, velocity, and length if you want Reynolds number estimates.
- Press the calculate button to display the result above the form.
- Review the graph, converted values, and supporting metrics.
- Use the CSV or PDF buttons to export the result summary.
Frequently Asked Questions
1. What is dynamic viscosity?
Dynamic viscosity measures a fluid’s internal resistance to flow. Higher values mean stronger resistance to deformation under shear. Common engineering units are Pa·s, cP, and P.
2. Why are cP and Pa·s both shown?
cP is centipoise, a practical unit for thin liquids. One Pa·s equals 1000 cP, and one poise equals 100 cP. Water near room temperature is close to 1 cP.
3. When should I use the shear-stress method?
Use the shear-stress method when laboratory rheometer data gives stress and shear rate. It is direct, simple, and ideal for Newtonian fluids over a measured operating range.
4. Does the pipe-flow method work for all flows?
The pipe-flow method assumes steady laminar flow in a circular tube. If turbulence appears, the Poiseuille relation no longer gives reliable viscosity values.
5. What is the difference between dynamic and kinematic viscosity?
Dynamic viscosity and kinematic viscosity are different. Dynamic viscosity measures resistance to shear, while kinematic viscosity equals dynamic viscosity divided by density.
6. Does temperature affect viscosity?
Temperature strongly changes viscosity. Liquids usually thin as temperature rises, while gases typically become more viscous. Always use measurements taken at a known temperature.
7. Why is Reynolds number included here?
Reynolds number helps judge whether flow is laminar or turbulent. This page estimates it only when density, characteristic length, and velocity are supplied.
8. How can I improve calculation accuracy?
For best accuracy, use consistent units, measured inputs, and realistic operating conditions. Check radius, gap, shear rate, and flow data carefully before interpreting results.