SixtyTools
Explore tools
Engineering & Science

Viscosity Converter

Convert viscosity in both of its forms. Dynamic (absolute) viscosity (μ) measures a fluid’s internal resistance to shear, in pascal-seconds or the centipoise familiar from oils — water is about 1 cP. Kinematic viscosity (ν) is dynamic viscosity divided by density, in square metres per second or centistokes, and is what falls out of many flow measurements. Converting within either form uses fixed ratios; crossing between them needs the fluid’s density, since ν = μ ÷ ρ.

How to use this tool

  1. Enter a viscosity value.
  2. Pick the unit you have and the unit you want — dynamic and kinematic units are grouped in the menus.
  3. When converting between a dynamic and a kinematic unit, enter the fluid density.
  4. Conversions within one form ignore the density.
  5. Read the result, with the density used shown when it applies.

The formula

Dynamic viscosity (μ) measures a fluid’s resistance to shear; kinematic viscosity (ν) is that divided by density. Within each the units are fixed ratios; converting between them needs the density.

ν = μ ÷ ρ μ = ν · ρ
μ
Dynamic viscosity, Pa·s
ν
Kinematic viscosity, m²/s
ρ
Density, kg/m³

Water at 20 °C is about 1 cP (0.001 Pa·s) dynamic, and about 1 cSt (1×10⁻⁶ m²/s) kinematic, because its density is close to 1000 kg/m³.

Worked examples

Water

Given
1 cP
Result
0.001 Pa·s

Water at 20 °C has a dynamic viscosity of about 1 centipoise, which is one millipascal-second.

Dynamic to kinematic

Given
1 cP water (ρ = 998)
Result
≈ 1.002 cSt

Dividing dynamic viscosity by density gives kinematic viscosity, so water is about 1 cP and 1 cSt together.

Motor oil

Given
0.25 Pa·s
Result
250 cP

A 0.25 Pa·s oil is 250 centipoise — far thicker than water, as engine oils are.

Frequently asked questions

Dynamic viscosity is the fluid’s resistance to shearing force; kinematic viscosity is that resistance relative to the fluid’s density (ν = μ/ρ). Kinematic viscosity governs how a fluid flows under gravity, which is why it appears in many flow and lubrication measurements.

Only to convert between a dynamic unit and a kinematic unit. Dynamic-to-dynamic and kinematic-to-kinematic conversions are fixed ratios. The tool applies the density only when the conversion crosses between the two forms.

Water at 20 °C is close to 1 cP dynamic and, because its density is near 1000 kg/m³, close to 1 cSt kinematic. The centipoise and centistokes were scaled so water comes out near 1 in each, which makes them convenient reference units.

They are the CGS units. One poise is 0.1 Pa·s and one stokes is 10⁻⁴ m²/s; the centipoise and centistokes are hundredths of those. They remain common in lubricant and process data despite SI being the formal standard.

Strongly. Liquids get much thinner as they warm — engine oil at operating temperature is a fraction of its cold viscosity. This tool converts a given value between units and forms; it does not model the temperature dependence, so use the viscosity at your actual conditions.

Flow Rate Converter

Convert volumetric and mass flow rate, with density-based conversion between them.

 Surface Tension & Permeability Converter

Convert surface tension (N/m, dyn/cm) and permeability (m², darcy).

 Specific Volume Converter

Convert specific volume between m³/kg, ft³/lb, L/kg and cm³/g — the reciprocal of density.