Poise Stokes Converter - Dynamic and Kinematic Viscosity Units

A poise stokes converter is a viscosity unit-conversion tool that switches between the CGS units poise (P) and stokes (St) and their SI counterparts pascal-second (Pa·s) and square metre per second (m²/s), with optional fluid density so the same input can move between the dynamic and kinematic families in a single step. It is built for fluid-mechanics homework, lab work, and engineering design where one source gives viscosity in centipoise and the next table needs centistokes.

• • Lab and textbook cross-checks: Confirm that a datasheet value in centipoise matches a textbook kinematic-viscosity chart in centistokes when you already know the fluid density.
• • Reynolds number setup: Convert a kinematic-viscosity spec into the dynamic-viscosity form needed when the rest of the pipe-flow problem is in SI units.
• • Pump and hydraulic calculations: Translate an oil grade expressed in centistokes into pascal-second for pressure-drop work.
• • Process engineering conversions: Switch between mm²/s and cSt (they are numerically identical) or between stokes and m²/s for CFD pre-processing.

Viscosity shows up in two forms: dynamic viscosity, which describes resistance to shear, and kinematic viscosity, which is dynamic viscosity divided by density. The poise and the stokes are the historical CGS units, while pascal-second and square metre per second are the modern SI units.

When a kinematic-viscosity value feeds straight into a flow-regime check, the Reynolds number calculator takes the same input and tells you whether the flow is laminar, transitional, or turbulent.

The calculator converts the input to the SI base unit of its viscosity family, optionally applies a density factor when crossing families, and rescales to the requested target unit.

• value: Numeric amount to convert. The input is parsed as a floating-point number; any non-finite input is treated as zero.
• factor_from: Multiplier that rescales the source unit into its family's SI base unit. For dynamic units: 0.1 for poise, 0.001 for centipoise, 1 for Pa·s, 0.001 for mPa·s. For kinematic units: 1e-4 for stokes, 1e-6 for centistokes, 1 for m²/s, 1e-6 for mm²/s.
• rho_SI: Fluid mass density in kg/m³, converted from g/cm³, kg/m³, or kg/L. It is only applied when the conversion crosses between the dynamic and kinematic families.
• factor_to: Multiplier that rescales the target SI value into the requested target unit, using the same factor table as factor_from but in the inverse direction.

The same-family dynamic and kinematic identities are exact: 1 P = 0.1 Pa·s, 1 cP = 1 mPa·s = 0.001 Pa·s, 1 St = 1e-4 m²/s, and 1 cSt = 1 mm²/s = 1e-6 m²/s. The only step that requires care is the density factor, applied only when the source and target live in different families.

According to Wikipedia, poise is the CGS unit of dynamic viscosity, defined as 1 gram per centimetre per second, and 1 poise equals 0.1 pascal-second

According to Wikipedia, stokes is the CGS unit of kinematic viscosity, defined as 1 square centimetre per second, and 1 stokes equals 1e-4 square metre per second

For pipe-flow work, the kinematic value the converter just produced feeds the Reynolds number that picks the laminar or turbulent branch of the Moody chart, and the friction factor calculator solves Colebrook-White with the same SI inputs you already have.

Four ideas behind the poise stokes converter worth understanding before you trust the numbers.

These four ideas explain why the same fluid can appear with very different numbers in different sources: the unit family, the unit system, the fluid density, and the measurement temperature are all baked in.

The same fluid density that crosses the dynamic and kinematic families also feeds the drag calculation, where the drag equation calculator uses it together with a Reynolds-regime hint to estimate the resistive force on a body moving through the fluid.

Use the poise stokes converter in five steps, treating the density field as required when the From and To units are not in the same family.

1. 1 Enter the value: Type the numeric amount in the Value to Convert field. Zero is a legal input and returns zero in the target unit.
2. 2 Pick the From Unit: Choose the source unit. Dynamic family options are poise, centipoise, Pa·s, mPa·s. Kinematic family options are stokes, centistokes, m²/s, mm²/s.
3. 3 Pick the To Unit: Choose the target unit. The same eight options are available. If the target is in the same family as the source, the density field is optional.
4. 4 Enter the fluid density when crossing families: If the From and To units are in different families, enter a positive fluid density and pick its unit. Water at 20°C is 0.998 g/cm³; air at sea level is about 0.001225 g/cm³.
5. 5 Read the converted value and the SI cross-check: The primary output shows the converted value in the chosen target unit. The secondary read-outs show the canonical pascal-second and square-metre-per-second values.

A pump datasheet lists a hydraulic oil at 32 centistokes with a density of 0.86 g/cm³, and you want the dynamic viscosity in millipascal-second. Enter 32, pick centistokes as the From Unit, pick mPa·s as the To Unit, and enter 0.86 in the density field. The calculator returns 27.52 mPa·s.

When the only density you can find is in pounds per gallon or kilograms per litre, the density calculator converts it into grams per cubic centimetre so the cross-family viscosity conversion can pick it up.

Practical reasons to use this poise stokes converter rather than a unit-rescale table or a hand calculation.

• • One tool for both CGS and SI: Eight viscosity units on each side cover poise, centipoise, stokes, centistokes, Pa·s, mPa·s, m²/s, and mm²/s, so most lab and engineering references are handled without a second lookup.
• • Density-aware cross-family conversion: The dynamic-to-kinematic step uses a single density input in g/cm³, kg/m³, or kg/L, so the same calculator handles water, oil, glycerol, and air.
• • Canonical SI values visible at the same time: The pascal-second and square-metre-per-second read-outs let you verify the result against an SI calculation, which is the format most textbooks and engineering tools use.
• • Fast, accurate identity shortcuts: Centipoise equals millipascal-second and centistokes equals square millimetre per second, so the calculator returns 1 for those same-unit pairs without rounding error.
• • Clear error handling for missing inputs: A cross-family conversion with a zero or missing density returns a clear error rather than a nonsense number, so the missing input is obvious.
• • Ties into force-balance and shear-stress work: Dynamic viscosity has units of N·s/m², so the pascal-second read-out becomes the coefficient that turns a velocity gradient into a shear-stress term.

For day-to-day fluid-mechanics problems the calculator is enough on its own: enter the value, pick the units, and the SI cross-check answers most sanity-check questions.

What changes the answer the poise stokes converter returns, and where the result is a unit conversion rather than a physical prediction.

• • The converter is a unit tool, not a viscosity predictor. It will faithfully convert 1 cP at 20°C to 1 mPa·s, but it will not warn you that water at 80°C has a dynamic viscosity closer to 0.355 cP.
• • A cross-family conversion with a missing or zero density cannot be completed because the relation ν = μ / ρ is undefined. The calculator flags this instead of returning a guessed number.

As published by the Engineering Toolbox, 1 cP equals 0.001 Pa·s and 1 cSt equals 1 mm²/s, and water at 20.2°C has a dynamic viscosity of exactly 1 centipoise, which is the anchor for the cP/cSt shortcut.

As published by Engineering Toolbox, 1 cP = 0.001 Pa·s, 1 cSt = 1 mm²/s = 1e-6 m²/s, and water at 20°C has a dynamic viscosity of 1 centipoise

When a viscous term shows up as a shear-stress coefficient in a momentum balance, the forces newtons laws calculator handles the matching F = ma side so inertial and viscous forces sit on the same free-body diagram.