What this calculator does
This tool computes the dynamic (absolute) viscosity of liquid water as a function of temperature. Enter a water temperature in degrees Celsius, Fahrenheit, or Kelvin and it returns the viscosity in millipascal-seconds (mPa·s, identical to centipoise), pascal-seconds (Pa·s, the SI unit), and poise (P). Water becomes noticeably thinner as it warms: near 0 °C it is almost twice as viscous as it is at body temperature.
How to use it
Type the water temperature into the input box and choose the matching unit (°C, °F, or K). The calculator converts the value to absolute temperature, applies the viscosity correlation, and shows the result. The correlation is intended for liquid water at temperatures from roughly 0 °C up to 370 °C (under pressure), which is why inputs far outside that band are rejected.
The formula explained
Viscosity is calculated with a widely used empirical Vogel-type correlation for water:
$$ \mu(T) = A \cdot 10^{ \frac{B}{\,T - C\,} } $$Here T is the absolute temperature in kelvin and the fitted constants are A = 2.414×10-5 Pa·s, B = 247.8 K, and C = 140 K. The result μ comes out in pascal-seconds; multiply by 1000 to get mPa·s (centipoise) or by 10 to get poise. The fit is accurate to about 1% between 0 and 100 °C, with slightly larger error very close to freezing.
Worked example
For water at 20 °C, first convert to kelvin: T = 20 + 273.15 = 293.15 K. Then evaluate the exponent, 247.8 / (293.15 − 140) = 1.618, so:
$$ \mu = 2.414 \times 10^{-5} \cdot 10^{ \frac{247.8}{\,293.15 - 140\,} } = 1.002 \times 10^{-3}\ \text{Pa s} $$That equals 1.002 mPa·s (or 1.002 cP), matching the textbook value for water at room temperature.
Frequently asked questions
Why does water's viscosity fall as temperature rises? Warming water gives its molecules more thermal energy, which weakens the hydrogen-bond network that resists flow, so the liquid becomes thinner and flows more easily.
What is the viscosity of water at room temperature? At 20 °C water has a dynamic viscosity of about 1.00 mPa·s, dropping to roughly 0.89 mPa·s at 25 °C.
Is dynamic viscosity the same as centipoise? Centipoise is a unit, not a different quantity: 1 mPa·s equals exactly 1 cP, so the dynamic viscosity expressed in cP is the same number shown in mPa·s.
