Pascal Seconds to Poise Converter
Common Conversions
| Pa·s | P |
|---|---|
| 0.001 | 0.01 |
| 0.005 | 0.05 |
| 0.01 | 0.1 |
| 0.05 | 0.5 |
| 0.1 | 1 |
| 0.2 | 2 |
| 0.5 | 5 |
| 1 | 10 |
| 5 | 50 |
| 10 | 100 |
Why this conversion matters in chemistry
Take cross-era polymer-melt math. A 0.5 Pa·s polymer-melt viscosity is 5 P — the form classical capillary-flow analysis in classical transport-phenomena texts reports the same quantity in. The 10 P per Pa·s is the gram-centimeter (CGS) versus kilogram-meter (SI) basis difference reduced to a single multiplier. Water at 20 °C provides the canonical anchor: 1.002 cP, equivalently 0.01002 P or about 1 mPa·s. In practice it's a unit handoff between legacy fluid-dynamics literature and modern SI rheology data.
Formula
Where the factor comes from
Written out in base units the two have the same shape: a pascal-second is a kilogram per meter-second, a poise a gram per centimeter-second. The factor is therefore the mass ratio divided by the length ratio — a thousand grams to the kilogram, but only a hundred centimetres to the meter — and the two partly cancel, leaving exactly 10 poise per pascal-second. That near-cancellation is the whole reason the poise sits one decade away rather than three, and it is worth holding onto, because the reflex that CGS units are always off by a thousand produces most of the errors on this pair. The gram-to-kilogram and centimeter-to-meter relations are prefix definitions, so the 10 is exact and contributes no uncertainty of its own.
Precision and significant figures
One decade, exact: the decimal point moves a single place right and the significant figures stay whatever the instrument supplied. That is also the practical case against the unit. Water at 25 °C reads 0.00089 Pa·s and becomes 0.0089 P, no easier to scan or compare than what you started with, which is precisely why nearly everyone works in centipoise instead. Where poise still earns its place is classical fluid-dynamics work, and values from that literature usually arrive already rounded to two or three figures — the shift must not be allowed to imply otherwise. Record the temperature too; a viscosity quoted without one is worth about a single significant figure.
Worked Examples
Water at 20 °C — equivalently 1 cP, the canonical anchor.
About a moderately viscous liquid — the conversion anchor.
Glycerol at 25 °C — useful as a high-viscosity reference.
Common mistakes
Converting the viscosity and nothing else
Poise belongs to a whole system. A Reynolds number or a Hagen-Poiseuille pressure drop worked in CGS wants density in g/cm³, lengths in cm and pressures in dyne/cm² as well. Shift only the viscosity into poise and leave the rest in SI and you get a number that raises no dimensional complaint and means nothing. Work through in one system, or convert the result rather than the inputs.
The awkward size invites a second shift
0.001 Pa·s becoming 0.01 P looks like a slip even though it is correct, and the reflex is to nudge it up to 1 — which is the centipoise value, reached without relabelling the column. Poise to centipoise is a further factor of 100. If your converted numbers keep landing near unity, check which of the two units the header is actually claiming.
A torque-floor reading converts just as cleanly
Rotational instruments lose resolution on thin samples because the torque drops below what the transducer can distinguish. A 0.0002 Pa·s result on a low-viscosity solvent may be sitting at that limit, and multiplying by 10 to reach 0.002 P neither improves it nor exposes the problem. The converted figure inherits every bit of the original uncertainty while looking tidier for having shed a leading zero.