Water Viscosity Calculator

Water Viscosity at Temperature

Viscosity measures a fluid's resistance to flow. Water becomes less viscous as temperature rises — warm water flows more easily than cold water. This calculator estimates both dynamic and kinematic viscosity from temperature.

Formulas

Dynamic viscosity (empirical):

$$\mu = 2.414 \times 10^{-5} \times 10^{247.8/(T + 133.15)}$$

Kinematic viscosity:

$$\nu = \frac{\mu}{\rho}$$

$\mu$ is in Pa·s (equivalent to N·s/m²), $\nu$ is in m²/s, $T$ is temperature in °C, and $\rho$ is water density from the temperature-dependent polynomial.

Practical Notes

At 20 °C, water dynamic viscosity is about 1.0 mPa·s and kinematic viscosity is about 1.0 mm²/s. These values matter in pipe flow, pump sizing, and Reynolds number calculations.

Frequently Asked Questions

What is the viscosity of water at 20 °C?

Dynamic viscosity is about 1.00 mPa·s (0.001 Pa·s). Kinematic viscosity is about 1.00 mm²/s (1.0 × 10⁻⁶ m²/s).

What is the difference between dynamic and kinematic viscosity?

Dynamic viscosity (μ) measures internal friction. Kinematic viscosity (ν = μ/ρ) divides by density and is used in flow equations like Reynolds number.

Does water viscosity increase or decrease with temperature?

It decreases. Hot water flows more easily than cold water because molecular attraction weakens at higher temperatures.

What units are used for water viscosity?

Dynamic: Pa·s or mPa·s (millipascal-seconds). Kinematic: m²/s or mm²/s. 1 mPa·s = 1 cP (centipoise); 1 mm²/s = 1 cSt (centistoke).

Why is density needed for kinematic viscosity?

Kinematic viscosity normalizes dynamic viscosity by density: ν = μ/ρ. It appears in the Navier-Stokes equations and Reynolds number Re = ρvL/μ = vL/ν.

Report

Water Viscosity at Temperature

Formulas

Practical Notes

Frequently Asked Questions

Related Tools

Recent Visits