Water Viscosity Calculator

Background.

Water near room temperature has a viscosity of almost exactly one millipascal-second, which is part of why the old centipoise unit felt so natural. That tidy figure hides how strongly the value depends on temperature. Water just above freezing is roughly 1.75 times as viscous as water at 20 °C, and water near boiling has a little over a quarter of the 20 °C value, so across the liquid range viscosity changes more than sixfold. Around room temperature it drops by about 2.4% for each degree of warming.

That sensitivity shows up wherever water moves slowly or through narrow spaces. Fine particles settle faster in warm water than in cold, because the settling speed given by Stokes' law is inversely proportional to viscosity. Groundwater passes more slowly through the same aquifer when it is cold. Flow meters and viscometers calibrated with water need its viscosity at the temperature of the test, not a single remembered number.

The page estimates dynamic viscosity from temperature with an empirical three-constant correlation, μ = 2.414 × 10⁻⁵ × 10^(247.8/(T − 140)) Pa·s, with T in kelvin, then divides by the density you enter to give kinematic viscosity, the form used in Reynolds numbers and pipe-friction charts. Both come out in the units engineers usually quote, mPa·s and mm²/s.

The correlation is meant for pure liquid water near atmospheric pressure between just above 0 °C and 100 °C. Against standard reference tables it agrees to within about 1% over most of that range and runs about 2% low close to freezing. It is not the IAPWS reference formulation used for certified property work, and it does not cover steam, salt water, supercooled water or high pressure.

What is water viscosity calculator?

Viscosity is a fluid's resistance to flow, the internal friction between layers sliding past one another. Dynamic viscosity, μ, is the shear stress needed per unit rate of shear, measured in pascal-seconds; for water it is normally quoted in millipascal-seconds, numerically the same as centipoise. Kinematic viscosity, ν, is dynamic viscosity divided by density, quoted in mm²/s, the same as centistokes. It describes how momentum spreads through the moving fluid and is the version that appears in the Reynolds number.

How to use this calculator.

1. 01Enter the water temperature in °C, between 0.01 and 100. Use the temperature of the water itself where it flows, which can differ a lot from the air around it.
2. 02Enter the density of water at that same temperature: 998.2 kg/m³ at 20 °C, close to 1,000 at 4 °C, about 983.2 at 60 °C and about 958.4 near 100 °C. Density affects only the kinematic result.
3. 03Use the dynamic viscosity in mPa·s for shear stress, lubrication or settling calculations. Multiply by 0.001 if a formula needs Pa·s.
4. 04Use the kinematic viscosity in mm²/s for Reynolds numbers and friction-factor charts. Multiply by 10⁻⁶ if a formula needs m²/s.

The formula.

μ = 2.414 × 10⁻⁵ × 10^(247.8 ÷ (T − 140)) Pa·s, where T is the absolute temperature in kelvin, °C + 273.15. The three constants are empirical: 2.414 × 10⁻⁵ Pa·s sets the overall scale, 247.8 K sets how steeply viscosity falls with temperature, and 140 K shifts the temperature origin so the curve bends the way water's does. As T rises, T − 140 grows, the exponent shrinks and viscosity drops, quickly near freezing and more gently near boiling. Kinematic viscosity is ν = μ ÷ ρ. The page multiplies μ by 1,000 to report mPa·s and ν by 10⁶ to report mm²/s. Temperature dominates the result; the density you enter moves only ν, and liquid water's density varies by only about 4% between 4 °C and 100 °C.

A worked example.

Frequently asked questions.

References& sources.

1. [1]International Association for the Properties of Water and Steam. IAPWS viscosity release 2008. Reference formulation for ordinary water substance. Retrieved 2026-08-06.
2. [2]NIST. Chemistry WebBook current 2026. Water thermophysical data. Retrieved 2026-08-06.
3. [3]OpenStax, Rice University. University Physics, 2016. Volume 1 mechanics and Volume 2 thermodynamics. Retrieved 2026-08-06.