🍯 Viscosity

Viscosity Converter

Convert dynamic viscosity and kinematic viscosity units — pascal-seconds, centipoise, poise, stokes and centistokes. Choose a category, enter a value and press Convert.

Written and reviewed by SM Arijul Islam · Last reviewed 28 October 2026 · Editorial standards · Report an error

About the viscosity converter

Dynamic viscosity describes how much force is needed to slide one layer of fluid over another, and its SI unit is the pascal-second. The older CGS unit, the poise, is still everywhere in industry, and 1 P = 100 cP, so centipoise and millipascal-second are exactly the same size.

Kinematic viscosity is dynamic viscosity divided by density. It is the quantity a capillary viscometer actually measures, and it is written in stokes and centistokes. Because of that division, dynamic and kinematic values cannot be swapped without knowing the fluid's density, so this page keeps the two families in separate categories.

Key equivalences

Relationships between common viscosity units
Unit	Equals
1 Pa·s	1 kg/(m·s) = 10 poise = 1,000 cP = 1,000 mPa·s
1 cP	1 mPa·s = 0.001 Pa·s
1 lb/(ft·s)	1.488164 Pa·s
1 lbf·s/ft²	47.880259 Pa·s
1 reyn	6,894.757 Pa·s = 1 lbf·s/in²
1 stokes	1 cm²/s = 100 centistokes
1 ft²/s	929.03 centistokes

Typical dynamic viscosities at about 20 °C

Approximate dynamic viscosities of common fluids and materials
Substance	Dynamic viscosity
Air	0.018 mPa·s
Water	1.002 mPa·s
Olive oil	about 84 mPa·s
Motor oil SAE 30	about 200 mPa·s
Glycerol	about 1,410 mPa·s
Honey	2,000 – 10,000 mPa·s
Peanut butter	about 250,000 mPa·s

Worked examples

Water at 20 °C is 1.002 mPa·s, which is the same as 1.002 cP or 0.001002 Pa·s.
A hydraulic oil rated at 46 cSt has a dynamic viscosity of about 0.040 Pa·s once you multiply by its density of around 0.87 g/cm³.
ISO VG 32 oil is roughly 32 cSt at 40 °C, which is 3.2 × 10⁻⁵ m²/s.
Honey at 5,000 cP is 5 Pa·s — five thousand times thicker than water.

How viscosity is actually measured

Dynamic viscosity is measured with a rheometer or a rotational viscometer: a spindle turns in the sample and the torque required is converted into a viscosity. Kinematic viscosity is measured by timing how long a fixed volume takes to flow through a calibrated capillary, which is why the result is quoted in mm²/s and why the test is so sensitive to temperature.

Industry also uses flow cups — the Ford cup, the Zahn cup, the ISO cup — which give a "cup seconds" figure rather than a physical unit. Cup seconds can only be compared using the same cup at the same temperature, and converting them to centistokes needs a calibration curve for that specific cup. Paint and coatings specifications often quote both.

Temperature is not a detail here. The viscosity of most liquids falls by several percent for every degree Celsius, so a reading at 21 °C can differ from one at 25 °C by more than 20 percent. Always record the temperature with the number: a viscosity without a temperature is only half a measurement.

Finally, not every liquid has a single viscosity. Water, mineral oil and most solvents are Newtonian — their viscosity is the same at any shear rate. Paint, ketchup, shampoo and drilling mud are shear-thinning, so their apparent viscosity depends on how vigorously they are stirred. This converter works on the number you give it; interpreting that number for a non-Newtonian fluid needs the shear rate as well.

Frequently asked questions

Are centipoise and mPa·s identical?

Yes, exactly. 1 cP = 1 mPa·s = 0.001 Pa·s, which is why the two names are used interchangeably in water treatment and food science.

Can I convert cSt to cP directly?

Only if you know the density: cP = cSt × density in g/mL. For water at 20 °C the numbers happen to match, which is a common source of confusion.

What is the Reynolds number connection?

Flow calculations use kinematic viscosity, because the Reynolds number compares inertia with viscous forces and density cancels out. That is why cSt appears on pump datasheets.

Why does viscosity fall as it heats?

Warm molecules slip past each other more easily, so both dynamic and kinematic viscosity drop sharply. That is why oil grades are always quoted at a stated temperature such as 40 °C or 100 °C.

Common mistakes to avoid

Treating poise as pascal-seconds. One poise is only 0.1 Pa·s.
Quoting a viscosity without a temperature, which changes the value several-fold for oils.
Assuming a thicker-looking liquid is more viscous. Density and viscosity are unrelated properties.
Applying capillary-tube results to non-Newtonian fluids such as ketchup or paint, whose viscosity depends on shear rate.

Sources and standards

Dynamic viscosity is measured in pascal seconds and kinematic viscosity in square metres per second, with the stokes retained for historical use. The SI Brochure and NIST SP 811 define those units, and the page notes that one centipoise equals one millipascal second exactly.