Pascal-second to Poise Converter
Quickly convert from Pascal-second to Poise.
How to convert
Formula:
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Viscosity describes a fluid's resistance to flow — a critical property in lubrication, food processing, pharmaceuticals, and fluid dynamics.
Where is it used?
• Lubrication & Tribology — Engine oils are graded by SAE viscosity class (e.g., 5W-30); the kinematic viscosity at 100 °C defines the grade. Choosing wrong viscosity causes wear or excess drag.
Examples:
• 1 Pa·s = 1,000 cP (mPa·s)
• 1 poise (P) = 100 cP = 0.1 Pa·s
Viscosity describes a fluid's resistance to flow — a critical property in lubrication, food processing, pharmaceuticals, and fluid dynamics. Converting between dynamic viscosity (Pa·s, cP, mPa·s) and kinematic viscosity (m²/s, cSt) is essential for engineers selecting lubricants, designing pumps, and calculating Reynolds numbers.
Viscosity comes in two related forms. Dynamic (absolute) viscosity (η) measures internal friction per unit area and velocity gradient; its SI unit is the Pascal-second (Pa·s), with the centipoise (cP or mPa·s) widely used in practice. Kinematic viscosity (ν) is dynamic viscosity divided by fluid density; its SI unit is m²/s, with the centistoke (cSt) the practical standard. Water at 20 °C has a dynamic viscosity of ~1 cP and a kinematic viscosity of ~1 cSt.
Where is it used?
- Lubrication & Tribology — Engine oils are graded by SAE viscosity class (e.g., 5W-30); the kinematic viscosity at 100 °C defines the grade. Choosing wrong viscosity causes wear or excess drag.
- Chemical & Process Engineering — Pump sizing, pipe pressure-drop calculations (Hagen-Poiseuille law), and mixing tank design all depend on accurate viscosity values.
- Food Science — Sauces, syrups, and dairy products are characterized by viscosity for quality control, pumpability, and consumer texture perception.
- Pharmaceuticals — Injection solutions must fall within narrow viscosity ranges to pass through needles safely; topical formulations require target viscosities for spreadability.
- Aerospace & Hydraulics — Hydraulic fluid viscosity must remain stable across a wide temperature range to ensure predictable system response in aircraft and heavy machinery.
Common Conversion Mistakes
Confusing dynamic and kinematic viscosity
Dynamic viscosity (Pa·s, cP) and kinematic viscosity (m²/s, cSt) are related by density but are not interchangeable. Kinematic viscosity = dynamic viscosity ÷ density. For water at 20 °C both happen to be ~1 in their respective cP/cSt units, but for oils with density ~0.9 g/cm³ the numbers diverge significantly.
Forgetting temperature dependence
Viscosity is extremely temperature-sensitive. Engine oil viscosity can change by an order of magnitude between −20 °C and 100 °C. Always specify the temperature at which a viscosity was measured; values given without temperature context are meaningless for engineering calculations.
Mixing up poise and centipoise
1 poise (P) = 100 centipoise (cP) = 0.1 Pa·s. The centipoise (cP) is the practical unit for most liquids. Water at 20 °C ≈ 1.002 cP; honey ≈ 2,000–10,000 cP. Confusing P with cP leads to 100× errors.
Ignoring non-Newtonian behavior
Many real fluids (paints, ketchup, blood, polymer solutions) are non-Newtonian: their viscosity changes with shear rate. A single viscosity number does not fully describe them. Always check whether a fluid is Newtonian before applying standard viscosity conversions.
Quick Reference Table
| From | To |
|---|---|
| 1 Pa·s | 1,000 cP (mPa·s) |
| 1 poise (P) | 100 cP = 0.1 Pa·s |
| 1 centipoise (cP) | 1 mPa·s |
| 1 m²/s | 1,000,000 cSt |
| 1 stoke (St) | 100 cSt = 1 cm²/s |
| Water at 20 °C | ~1 cP dynamic, ~1 cSt kinematic |
| Olive oil at 20 °C | ~84 cP dynamic |
| SAE 30 oil at 100 °C | ~10 cSt kinematic |
Frequently Asked Questions
What is the difference between dynamic and kinematic viscosity?
Dynamic viscosity (η, Pa·s or cP) measures the force needed to shear a fluid at a given rate — it reflects the fluid's intrinsic resistance to flow. Kinematic viscosity (ν, m²/s or cSt) is dynamic viscosity divided by density (ν = η/ρ). Kinematic viscosity is used when gravity drives the flow (e.g., falling-ball viscometers, pipe flow under gravity), while dynamic viscosity is used in force and pressure calculations.
Why are SAE oil grades not simple viscosity numbers?
SAE grades like 5W-30 describe a multi-grade oil: the 'W' number (winter) indicates cold-start viscosity at low temperature (5W means the oil behaves like a 5-weight oil at −30 °C), and the second number (30) describes kinematic viscosity at 100 °C. Multi-grade oils use viscosity index improvers to stay fluid when cold and thick enough when hot.
How do I convert between dynamic and kinematic viscosity?
ν (cSt) = η (cP) ÷ ρ (g/cm³). For water at 20 °C: ν = 1.002 cP ÷ 0.998 g/cm³ ≈ 1.004 cSt. For a hydraulic oil with η = 46 cP and ρ = 0.875 g/cm³: ν = 46 ÷ 0.875 ≈ 52.6 cSt (an ISO VG 46 grade oil).
What is the Reynolds number and how does viscosity affect it?
The Reynolds number Re = ρvD/η = vD/ν determines whether flow is laminar (Re < 2,300) or turbulent (Re > 4,000) in a pipe. Higher viscosity reduces Re and promotes laminar flow. For pipe design, knowing the kinematic viscosity at the operating temperature is essential for predicting pressure drop and pumping power.
Sources & Standards
- ASTM D445 — Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids
- ISO 3104 — Petroleum products: kinematic viscosity measurement
- SAE J300 — Engine Oil Viscosity Classification
- National Institute of Standards and Technology (NIST) Reference Fluid Data
Reviewed by The Unit Hub Editorial Team · March 2026