Understanding dynamic viscosity
Dynamic viscosity is the fluid property that answers “how stiff is the shear?” It shows up wherever you relate stress in the fluid to how quickly velocity changes across a gap. Engineers live in pascal seconds or centipoise; older references still whisper in poise and pound foot second silliness. This tool parks everything beside the SI row so Reynolds numbers and pump curves stop arguing.
How dynamic viscosity conversion works
One pascal second equals one newton second per square meter. One poise is exactly 0.1 Pa·s, which is why centipoise lines up neatly at millipascal seconds for waterish liquids around room temperature.
Result = Value × (source as Pa·s per unit) ÷ (target as Pa·s per unit)
Imperial rows lean on the international inch and pound definitions you already tolerate in pressure converters. Slug-based entries match the usual mechanical engineering tables even if nobody orders slugs at the deli.
Units worth bookmarking
The menu lists the whole poise ladder for completeness. Start here before you chase yoctopoise novelty entries.
Pascal second [Pa·s]
Factor: 1 (base)
SI home base. Drops straight into textbook definitions with shear stress over velocity gradient.
Centipoise [cP]
Factor: 0.001 Pa·s per cP
Datasheets for oils, syrups, and coatings often quote this. About one millipascal second for mental rounding near water.
Poise [P]
Factor: 0.1 Pa·s per poise
CGS roots. Multiply poise by 100 to reach centipoise without drama.
Dyne second per square centimeter
Factor: lines up with 0.1 Pa·s
Older academic homework loves this packaging. Same neighborhood as poise once you unwrap units carefully.
Pound-force second per square foot
Factor: imperial force over square foot basis
Shows up inside certain pipe flow correlations and legacy pump manuals printed east of the Atlantic sometimes too.
Pound per foot hour
Factor: tiny Pa·s once hours unwind
Thin films and gases occasionally arrive here. Double-check whether the author meant dynamic or kinematic cousins before you paste numbers.
Common dynamic viscosity conversions at a glance
Ratios people scribble on duct liner when Wi-Fi dies.
| From | To | Pattern | Example |
|---|---|---|---|
| cP | Pa·s | ÷ 1000 | 1 cP = 0.001 Pa·s |
| P (poise) | Pa·s | ÷ 10 | 1 P = 0.1 Pa·s |
| mPa·s | cP | 1:1 numeric | About 1 for cool water |
| N·s/m² | Pa·s | same unit | Literally identical |
| dyn·s/cm² | Pa·s | ÷ 10 vs poise path | Matches poise chain |
| lb/(ft·s) | Pa·s | slug/ft scale | Use tool for constants |
Pairing with density for kinematic viscosity
Divide dynamic viscosity by mass density and you land in kinematic viscosity (length squared per time). That jump is safe only when ρ is the density of the fluid carrying the shear, not a random handbook value from a different temperature block.
Non-Newtonian fluids laugh at single-number viscosity. The value you convert might be a point on a curve, so keep the shear rate note next to the number when you archive it.
Dynamic viscosity FAQ
Are Pa·s and centipoise related cleanly?
Yes: multiply centipoise by 0.001 for pascal seconds. Water near 20 °C sits close to 1 cP, which is a handy sanity anchor.
Why so many poise prefixes?
Some catalogs chase extremes from polymer melts to gases. Pick the closest prefix your spreadsheet tolerates without scientific notation overload.
Does temperature matter?
Huge for real fluids. Conversion math only swaps labels; it does not guess viscosity at your operating point.
Which row matches my CFD package?
Most solvers ingest Pa·s internally. Export to centipoise only when humans must read the column.