What is the difference between dynamic and kinematic viscosity?

Dynamic viscosity measures a fluid’s internal resistance to shear and is expressed in Pa·s, mPa·s, centipoise or poise. Kinematic viscosity is the ratio of dynamic viscosity to density and is expressed in m2/s, Stokes or centistokes. Kinematic viscosity depends only on the type of fluid, not its density.

How do I convert from Pa·s to centipoise (cP)?

1 Pa·s corresponds to 1000 cP. To convert from Pa·s to cP, multiply by 1000. To convert from cP to Pa·s, divide by 1000. For example, 0.001 Pa·s = 1 cP, and 250 cP = 0.25 Pa·s.

How are dynamic and kinematic viscosity related?

Kinematic viscosity equals dynamic viscosity divided by fluid density. In SI units the relationship is: kinematic viscosity [m2/s] = dynamic viscosity [Pa·s] / density [kg/m3]. For example, water at 20°C has a dynamic viscosity of about 1 mPa·s and density of about 998 kg/m3, giving a kinematic viscosity close to 1.0×10−6 m2/s.

What is the typical viscosity of water at room temperature?

At around 20°C, liquid water has a dynamic viscosity of roughly 1 mPa·s, which is equivalent to 1 cP, and a kinematic viscosity of roughly 1.0×10−6 m2/s or 1 cSt. Exact values depend slightly on temperature and purity.

Which viscosity units are most common in engineering practice?

In SI-based work, Pa·s and mPa·s are standard for dynamic viscosity. In many industries, centipoise (cP) remains popular. For kinematic viscosity, centistokes (cSt) and mm2/s are widely used. Legacy CGS units such as poise and Stokes appear in older literature and some datasheets.

Viscosity Converter – Dynamic & Kinematic (Pa·s, cP, St, cSt)

Convert viscosity between the most common engineering units: Pa·s, mPa·s, centipoise (cP), poise (P), Stokes (St), centistokes (cSt), mm²/s and more. You can also convert between dynamic and kinematic viscosity using fluid density.

Designed for mechanical, chemical and process engineers working with pump sizing, lubrication, mixing and CFD simulations.

Viscosity conversion tool

Engineering grade

Dynamic viscosity unit converter

Dynamic viscosity describes the internal resistance to shear. Common units include Pa·s, mPa·s, cP and poise.

Value

From unit

To unit

Result

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Reference: 1 cP = 1 mPa·s = 0.001 Pa·s. 1 P = 0.1 Pa·s. 1 kg/(m·s) = 1 Pa·s.

Water at 20 °C ≈ 1 mPa·s (1 cP).

Dynamic ↔ kinematic viscosity (with density)

Kinematic viscosity ν is related to dynamic viscosity μ and density ρ by: ν [m²/s] = μ [Pa·s] / ρ [kg/m³].

Conversion direction

Viscosity value

Viscosity unit

Density ρ (kg/m³)

Use density at the same temperature as your viscosity data (from datasheets or handbooks).

Result

–

Example: water at 20 °C, μ ≈ 1 mPa·s, ρ ≈ 998 kg/m³ ⇒ ν ≈ 1.0×10⁻⁶ m²/s ≈ 1 cSt.

For oils and mixtures, always use the density provided by the manufacturer at the test temperature.

Understanding viscosity and its units

Viscosity measures how resistant a fluid is to motion. Honey has a high viscosity and flows slowly, while water has a low viscosity and flows easily. In engineering calculations you will typically encounter two related quantities:

Dynamic viscosity μ – resistance to shear, measured in Pa·s or mPa·s (SI) and in poise or centipoise (CGS).
Kinematic viscosity ν – dynamic viscosity divided by density, measured in m²/s, St or cSt.

Relationship between dynamic and kinematic viscosity

Using SI units:

ν [m²/s] = μ [Pa·s] / ρ [kg/m³]

where μ is dynamic viscosity and ρ is density. For water at 20 °C, μ ≈ 1 mPa·s and ρ ≈ 998 kg/m³, giving ν ≈ 1.0×10⁻⁶ m²/s = 1 cSt.

Main dynamic viscosity units

Pa·s (pascal-second): SI unit of dynamic viscosity.
mPa·s (millipascal-second): 1 mPa·s = 0.001 Pa·s. Numerically equal to centipoise.
cP (centipoise): legacy CGS unit; 1 cP = 1 mPa·s = 0.001 Pa·s.
P (poise): 1 P = 0.1 Pa·s = 100 cP.
kg/(m·s) or N·s/m²: equivalent to Pa·s in SI base units.

Main kinematic viscosity units

m²/s: SI unit of kinematic viscosity.
St (stokes): 1 St = 1 cm²/s = 1×10⁻⁴ m²/s.
cSt (centistokes): 1 cSt = 1 mm²/s = 1×10⁻⁶ m²/s.
mm²/s: frequently used in oil and lubricant datasheets; numerically equal to cSt.

Typical viscosity values

Below are order-of-magnitude values to quickly sanity-check your calculations (exact values depend on temperature and composition):

Air at 20 °C: μ ~ 0.018 mPa·s, ν ~ 15 cSt.
Water at 20 °C: μ ~ 1 mPa·s (1 cP), ν ~ 1 cSt.
Light oil at 40 °C: ν ~ 10–30 cSt.
Heavy gear oil at 40 °C: ν ~ 150–320 cSt.
Glycerin at 20 °C: μ ~ 1–1.5 Pa·s (1000–1500 cP).

How this viscosity converter works

1. Dynamic viscosity conversions

The dynamic viscosity converter uses Pa·s as the internal reference unit. Each unit is converted to Pa·s using standard factors (for example, 1 cP = 0.001 Pa·s, 1 P = 0.1 Pa·s) and then into the target unit. This approach minimizes rounding errors and keeps the logic transparent.

2. Kinematic viscosity conversions

The kinematic converter uses m²/s as the reference. For example, 1 cSt = 1 mm²/s = 1×10⁻⁶ m²/s, and 1 St = 1×10⁻⁴ m²/s. Conversions between cSt, St, mm²/s and m²/s are therefore straightforward and numerically stable.

3. Dynamic ↔ kinematic conversions

To move between dynamic and kinematic viscosity, the tool applies the textbook formula ν = μ / ρ. It first converts your input to either Pa·s (for dynamic) or m²/s (for kinematic), then divides or multiplies by density to obtain the desired result.

Good practices when working with viscosity

Always check temperature: viscosity is highly temperature-dependent. Use values measured or tabulated at the operating temperature.
Keep units consistent: especially when mixing data from datasheets, handbooks and simulations.
Use density from the same source: for dynamic ↔ kinematic conversions, density should be specified at the same temperature.
Sanity-check results: compare with typical ranges for similar fluids to detect typos or unit mix-ups.

Frequently asked questions about viscosity conversions

Is centipoise (cP) the same as mPa·s? ▾

Yes. By definition, 1 cP = 1 mPa·s. Many datasheets prefer cP, while SI-oriented documents may use mPa·s. Numerically they are identical, so you can freely switch between them.

When should I use kinematic instead of dynamic viscosity? ▾

Kinematic viscosity is convenient when density is already implicit or fixed, for example in lubrication standards and many pump correction charts. Dynamic viscosity is preferred in fundamental fluid mechanics equations and CFD models. You can use this calculator to move between the two when needed.

What if the datasheet gives viscosity in SSU, Engler or Saybolt units? ▾

These are older instrument-based viscosity scales based on flow time through standardized orifices. To use them in calculations, first convert them to cSt or cP using the correlations or charts provided by the manufacturer or standard, then use this converter to obtain Pa·s, m²/s or other engineering units.

How accurate is this converter for design work? ▾

The conversion factors are exact or defined constants, so numerical conversions are precise. The main source of uncertainty is the underlying viscosity and density data, especially if taken from approximate charts or at mismatched temperatures. For critical designs, always refer to manufacturer data and, where possible, lab measurements.

Can I use this tool for non-Newtonian fluids? ▾

You can convert reported viscosity values for non-Newtonian fluids, but remember that their apparent viscosity depends on shear rate and measurement method. The converter does not model shear-thinning or shear-thickening behaviour; it simply transforms numerical values between unit systems.