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Viscosity Converter

Converters · Added

Viscosity is two quantities rather than one. Dynamic viscosity measures resistance to shear; kinematic viscosity is that divided by density. Each converts within itself here, and deliberately not across — turning centipoise into centistokes needs the density of your particular fluid at your particular temperature.

Which viscosity?

Kinematic viscosity is dynamic viscosity divided by density, so turning centipoise into centistokes needs the density of your particular fluid at your particular temperature. That is not something a unit converter can know, so each quantity converts only within itself. Divide by density in kg/m³ and multiply by 10⁶ to go from mPa·s to cSt by hand.

Result

1 cP in pascal-second

0.001 Pa·s

1 cP = 0.001 Pa·s

The same value in every unit

Pascal-second (Pa·s)
0.001
Millipascal-second (mPa·s)
1
Kilogram per metre-second (kg/(m·s))
0.001
Poise (P)
0.01
Centipoise (cP)
1
Dyne-second per square centimetre (dyn·s/cm²)
0.01
Pound-force second per square foot (lbf·s/ft²)
0.0000208854342
Pound-force second per square inch (reyn) (reyn)
1.4504e-7
Pound per foot-second (lb/(ft·s))
0.000671968975
Pound per foot-hour (lb/(ft·h))
2.41908831
Kilogram-force second per square metre (kgf·s/m²)
0.000101971621

Dynamic viscosity, also called absolute viscosity. One poise is exactly 0.1 Pa·s by the CGS definition, so a centipoise is exactly one millipascal-second — water at 20 °C sits within a per cent of both.

How to use the viscosity converter

  1. 1Choose whether you are working with dynamic or kinematic viscosity.
  2. 2Enter the value and pick the unit it is in.
  3. 3Pick the unit you want it in — the full conversion table appears underneath.
  4. 4To cross between the two quantities, divide or multiply by the fluid's density yourself.

Examples

Water at room temperature

Input
1 cP
Result
0.001 Pa·s

Water at 20 °C is almost exactly one centipoise, which is why the unit has outlived its SI replacement.

An engine oil specification

Input
10 cSt
Result
1 × 10⁻⁵ m²/s

About the viscosity converter

What the two quantities actually measure

Dynamic viscosity is the resistance a fluid puts up against being sheared: push one layer past another and this is what pushes back. It is the quantity that appears in the equations for pressure drop in a pipe and drag on a surface.

Kinematic viscosity is that same resistance divided by the fluid's density, which turns it into a measure of how readily the fluid flows under its own weight. It is what a flow cup or a capillary viscometer measures directly, and it is why oil grades are quoted in centistokes rather than centipoise.

The reyn, and other units worth recognising

The reyn — pound-force second per square inch — turns up in bearing and lubrication work and is enormous compared with everything else: one reyn is nearly 6,900 Pa·s. Seeing a figure of 2 × 10⁻⁶ reyn rather than 2 reyn is normal.

On the kinematic side, the Saybolt Universal Second appears in older American oil specifications. It is not a unit of the same kind: it is a timed flow through a specific orifice, and converting it needs an empirical formula rather than a factor, which is why it is not offered here.

Frequently asked questions

Why can it not convert centipoise to centistokes?
Because the two describe different quantities and the bridge between them is density. Dividing dynamic viscosity in Pa·s by density in kg/m³ gives kinematic viscosity in m²/s, and the density depends on which fluid you have and how warm it is. A converter that offered the conversion would be quietly inventing a number for it.
How do I make that conversion myself?
Divide the dynamic viscosity by the density in consistent units. Working in mPa·s and kg/m³, dividing and multiplying by a thousand gives centistokes. For water at 20 °C: 1.002 mPa·s divided by 998.2 kg/m³ gives 1.004 cSt, which is why the two figures look almost the same for water and diverge sharply for anything denser or lighter.
Is the poise still used?
Constantly, in the form of the centipoise. It is a CGS unit that SI formally replaced, but a scale on which water sits at 1 is too convenient to give up, so paint, ink, food, adhesive and polymer specifications are still written in cP. The definition is exact — one poise is 0.1 Pa·s — so nothing is lost in converting.
Does temperature matter?
Enormously, and more than for almost any other property. Engine oil can be several hundred times more viscous cold than hot, and a ten-degree change moves most liquids appreciably. A viscosity figure without a temperature attached is incomplete, and this converter changes units without knowing anything about temperature.

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