Dynamic viscosity — a fluid's resistance to flow — is measured in a mix of units depending on the field and era. Chemistry and rheology often use poise or centipoise, engineering specs often use the SI pascal-second, and older US customary references sometimes use pound-force-second per square foot. This converter translates between all four so you can compare a lubricant spec, a food-science reading, or a textbook problem without doing the math by hand.
Why viscosity has so many units
The SI unit for dynamic viscosity is the pascal-second (Pa·s), but it rarely shows up on consumer or industrial spec sheets because it produces awkward numbers for common fluids — water's viscosity is 0.001 Pa·s, a value few people find intuitive. Centipoise avoids this problem: water comes out to almost exactly 1 cP, which is why centipoise became the default unit in food science, cosmetics, paints, and coatings. Poise (100 times larger than centipoise) persists in older chemistry literature and some CGS-unit engineering contexts. Pound-force-second per square foot occasionally appears in US customary engineering references, particularly older fluid-mechanics textbooks and some petroleum-industry documents.
How the conversion works
This calculator converts every unit through a single common base — the pascal-second (Pa·s), the SI unit for dynamic viscosity. Your input value is first converted to Pa·s using that unit's fixed factor, then converted from Pa·s into the target unit. This two-step approach means adding a new unit only requires one conversion factor, and it guarantees that converting A → B gives the same answer as converting A → Pa·s → B, with no rounding surprises from unit-pair-specific shortcuts.
Dynamic vs. kinematic viscosity
This tool converts dynamic viscosity (also called absolute viscosity), which measures resistance to flow independent of the fluid's density. A separate, related quantity — kinematic viscosity — divides dynamic viscosity by density (ν = μ / ρ) and is typically reported in centistokes (cSt) or square meters per second. The two are easy to confuse because both show up on fluid datasheets, but they answer different questions: dynamic viscosity describes the force needed to shear the fluid, while kinematic viscosity describes how the fluid flows under gravity alone. If your datasheet gives kinematic viscosity, you'll need the fluid's density to convert it to the dynamic-viscosity units this calculator handles.