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Viscosity Converter

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Dynamic Viscosity Conversion

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Common Conversions

1 cP → Pa·s

1 cP = 0.001 Pa·s

1 P → cP

1 P = 100 cP

1 cSt → m²/s

1 cSt = 10⁻⁶ m²/s

1 St → cSt

1 St = 100 cSt

About This Tool

Viscosity Converter – Dynamic and Kinematic Viscosity Units

The Viscosity Converter lets you instantly convert between all major viscosity units used in engineering, science, and industry. It covers two independent measurement categories — dynamic viscosity and kinematic viscosity — with full support for SI units (Pa·s, m²/s), CGS units (Poise, Stokes), and Imperial/US units (lb/(ft·s), ft²/s). Whether you are working in fluid mechanics, lubrication engineering, food science, or chemical processing, this tool gives you accurate results with adjustable decimal precision.

Dynamic Viscosity vs. Kinematic Viscosity

Viscosity describes how strongly a fluid resists deformation under shear stress. Two related but distinct quantities are used to characterise this resistance:

  • Dynamic viscosity (also called absolute viscosity) measures the force needed to move a fluid layer at a given speed relative to an adjacent layer. Its SI unit is the Pascal-second (Pa·s), and the practical CGS unit is the centipoise (cP) — where 1 cP = 1 mPa·s exactly. Water at 20 °C has a dynamic viscosity of approximately 1 cP, making centipoise a convenient reference point.
  • Kinematic viscosity is the ratio of dynamic viscosity to fluid density: ν = μ / ρ. It represents how quickly momentum diffuses through a fluid under gravity. Its SI unit is m²/s, and the practical CGS unit is the centistoke (cSt) — where 1 cSt = 1 mm²/s exactly. Water at 20 °C has a kinematic viscosity of approximately 1 cSt.

Because kinematic viscosity incorporates density, it cannot be converted to dynamic viscosity without knowing the fluid density at a specific temperature. This tool keeps the two categories independent.

How the Converter Works

All conversions use a two-step normalisation approach. Each unit is defined by its factor relative to the SI base unit of its category. To convert from unit A to unit B:

  1. Multiply the input value by unit A's conversion factor to reach the SI base (e.g., 1 cP × 0.001 = 0.001 Pa·s).
  2. Divide the base-unit value by unit B's factor (e.g., 0.001 Pa·s ÷ 0.1 = 0.01 P).

This gives 1 cP = 0.01 P, which matches the known relationship. The same pattern applies across all units in each category.

Key Dynamic Viscosity Conversions

  • 1 Pa·s = 10 P = 1000 cP (exact)
  • 1 cP = 1 mPa·s (exact) — water at 20 °C
  • 1 lb/(ft·s) ≈ 1.4882 Pa·s — common in US engineering
  • 1 reyn = 1 lbf·s/in² ≈ 6894.76 Pa·s — used for heavy lubricants

Key Kinematic Viscosity Conversions

  • 1 m²/s = 10⁴ St = 10⁶ cSt (exact)
  • 1 cSt = 1 mm²/s (exact) — water at 20 °C
  • 1 ft²/s ≈ 929 St ≈ 92,900 cSt — Imperial unit
  • 1 St = 100 cSt (exact) — CGS relationship

Common Viscosity Reference Values

Understanding the scale of your result is easier with reference values. Air at 25 °C has a dynamic viscosity of about 18.5 µPa·s, making it far less viscous than water. Olive oil at 20 °C is roughly 80–100 cP, honey ranges from 2,000–10,000 cP, and heavy gear oils can exceed 1,000,000 cP at low temperatures. In lubrication engineering, ISO viscosity grades (ISO VG 32, VG 46, VG 100, etc.) specify kinematic viscosity in cSt at 40 °C, so the cSt unit is fundamental for selecting hydraulic fluids and gear oils.

Industrial and Scientific Applications

Viscosity conversions appear in many engineering disciplines:

  • Petroleum engineering — crude oil viscosity in cP or cSt determines pipeline design, pump selection, and flow assurance strategies.
  • Lubrication — ISO VG grades and SAE motor oil grades are defined in cSt, but manufacturers often report in cP at operating temperature.
  • Food science — sauces, syrups, and dairy products are characterised in cP or mPa·s for quality control and process design.
  • Pharmaceuticals — injectables and topical formulations must meet viscosity specifications for safe administration and proper texture.
  • Aerodynamics — kinematic viscosity in m²/s or ft²/s is used directly in the Reynolds number, which governs laminar vs. turbulent flow.
  • Chemical processing — reactor and mixer designs rely on accurate viscosity values to determine heat transfer coefficients and mixing energy.

Using the Tool

Select a viscosity type using the tabs at the top: Dynamic Viscosity or Kinematic Viscosity. Enter a numeric value, choose the source and target units from the drop-down menus, and the result updates immediately. Enable the “Show all unit conversions” toggle to see your input expressed in every available unit of the selected category — useful for comparing scales at a glance. Use the Swap button to reverse the conversion direction, and Copy Result to copy the output to your clipboard.

Frequently Asked Questions

Is the Viscosity Converter free?

Yes, Viscosity Converter is totally free :)

Can I use the Viscosity Converter offline?

Yes, you can install the webapp as PWA.

Is it safe to use Viscosity Converter?

Yes, any data related to Viscosity Converter only stored in your browser (if storage required). You can simply clear browser cache to clear all the stored data. We do not store any data on server.

How does this viscosity converter work?

The tool converts values within two independent viscosity categories: Dynamic Viscosity and Kinematic Viscosity. Within each category, every conversion normalises through an SI base unit — Pascal-second (Pa·s) for dynamic viscosity and square meter per second (m²/s) for kinematic viscosity. The input value is multiplied by the source unit's conversion factor to reach the base unit, then divided by the target unit's factor to produce the result.

What is the difference between dynamic and kinematic viscosity?

Dynamic viscosity (also called absolute viscosity) measures a fluid's resistance to flow under an applied shear stress; its SI unit is the Pascal-second (Pa·s). Kinematic viscosity is the ratio of dynamic viscosity to fluid density; its SI unit is m²/s. Kinematic viscosity is more convenient when the density is already factored in, such as in pipe flow calculations and lubrication standards. The two quantities cannot be freely converted without knowing the fluid density.

What are the most common viscosity units in practice?

For dynamic viscosity, the centipoise (cP) is the most widely used practical unit — water at 20 °C is approximately 1 cP. For kinematic viscosity, the centistoke (cSt) dominates in lubrication and petroleum engineering; ISO viscosity grades (e.g., ISO VG 46) are defined in cSt at 40 °C. In scientific literature, Pa·s and m²/s are the SI standard.

Why can't I convert between dynamic and kinematic viscosity?

Converting between dynamic viscosity (Pa·s or cP) and kinematic viscosity (m²/s or cSt) requires the fluid density at a specific temperature. The relationship is: kinematic viscosity = dynamic viscosity ÷ density. Because density varies by fluid and temperature, this conversion cannot be performed with a fixed constant. Each category is kept independent in this tool.

What are Poise and Stokes, and are they still used?

Poise (P) and centipoise (cP) are CGS units of dynamic viscosity, where 1 P = 0.1 Pa·s and 1 cP = 1 mPa·s. Stokes (St) and centistokes (cSt) are CGS units of kinematic viscosity, where 1 St = 10⁻⁴ m²/s and 1 cSt = 1 mm²/s. Although SI units are preferred in scientific work, cP and cSt remain in widespread use in industry, food science, and petroleum engineering.

Are the conversion results accurate for professional use?

Yes. All conversion factors are based on exact SI definitions and NIST/ISO standards: 1 cP = exactly 1 mPa·s; 1 cSt = exactly 1 mm²/s; 1 P = exactly 0.1 Pa·s; 1 St = exactly 10⁻⁴ m²/s. Imperial conversions use the standard international definitions of pound, foot, and inch. Calculations use IEEE 754 double-precision floating-point arithmetic (approximately 15 significant digits of precision).