Centipoise to Pascal-Seconds Viscosity Converter
Common Conversions
| cP | Pa·s |
|---|---|
| 0.1 | 0.0001 |
| 0.5 | 0.0005 |
| 1 | 0.001 |
| 2 | 0.002 |
| 5 | 0.005 |
| 10 | 0.01 |
| 25 | 0.025 |
| 50 | 0.05 |
| 100 | 0.1 |
| 1000 | 1 |
Why this conversion matters in chemistry
The centipoise survives in chemistry because of one convenient coincidence: water at 20 °C is almost exactly 1 cP. Other common values fall on a familiar scale — ethanol at about 1.2, glycerol at 1412 (20 °C). Pascal-seconds are the SI base unit for dynamic viscosity, but the numbers come out as awkward decimals. The conversion is a clean factor of 1000 — 1 cP equals 1 mPa·s — which falls out of the translation between dyne·s/cm² in CGS and N·s/m² in SI. Multiplying by 10⁻³ is the standard step before any Reynolds-number or fluid-dynamics calculation that wants base SI throughout.
Formula
Where the factor comes from
Both units express the same physical definition — a shear stress divided by a velocity gradient — and differ only in which system supplies the stress and the length. The poise is a dyne-second per square centimeter. A dyne is exactly 10⁻⁵ newtons and a square centimeter exactly 10⁻⁴ square meters, so a poise is 10⁻⁵ ÷ 10⁻⁴ = 0.1 pascal-second, exactly. Apply centi, exactly 10⁻², and a centipoise is exactly 10⁻³ Pa·s. Which is to say a centipoise and a millipascal-second are one unit under two names, and this conversion is a relabeling rather than a calculation. Every quantity in that chain is a definition rather than a measurement, so the factor carries no uncertainty of any kind.
Precision and significant figures
Because the factor is exact, the whole precision question falls onto the viscosity value itself — where it belongs, viscosity being among the more temperature-sensitive properties on the bench. Water near room temperature sheds roughly two percent of its viscosity per kelvin, so a figure quoted to four significant figures with no temperature attached is worth about one. Water at 20 °C is close to 1.00 mPa·s but not exactly 1; the centipoise was sized to make that nearly true, not exactly so. Record the temperature alongside any converted value, and let significant figures follow the measurement — capillary and rotational instruments typically deliver three at best on a well-controlled sample.
Worked Examples
Water at 20 °C — the conversion's calibration anchor and the reason the centipoise is sized the way it is.
Glycerol at 20 °C — a thousand-fold more viscous than water, useful as a reference for high-viscosity fluids.
Acetone at 20 °C — at the low-viscosity end of common organic solvents.
Common mistakes
Centistokes measure kinematic viscosity, not dynamic
A centistokes is a kinematic viscosity, dynamic viscosity divided by density, and converts to 10⁻⁶ m²/s rather than to Pa·s. Water hides the distinction because its density is near 1 g/cm³, making its cP and cSt values nearly equal. For anything denser or lighter the two diverge, and applying the cP factor to a cSt figure silently drops the density.
Poise and centipoise differ by 100
Older literature reports in poise rather than centipoise, and the two are easy to conflate when the unit is abbreviated to P or cP in a table header. A poise is 0.1 Pa·s, a centipoise 0.001 Pa·s. Applying the centipoise factor to a value tabulated in poise puts the viscosity a hundredfold low with no dimensional clue that anything went wrong.
Non-Newtonian fluids have no single viscosity
Polymer solutions, slurries and gum thickeners shear-thin, so the measured viscosity depends on the shear rate the instrument applied. A cP value from such a fluid carries that shear rate implicitly. Converting it to Pa·s is arithmetically exact, but comparing two converted values taken at different shear rates compares nothing meaningful.