Water Viscosity Calculator for Dynamic and Kinematic

A water viscosity calculator converts a water temperature, anywhere from 0°C (the ice point) to 100°C (boiling at one atmosphere), into the liquid's dynamic and kinematic viscosity. It answers the practical question of what the viscosity of water actually is at the exact temperature you are working with, instead of forcing you to read a printed table only at the nearest listed grid point. Viscosity is the internal friction that resists flow, so knowing it lets you predict how fast water drains through a pipe, how hard a pump must work, or how a fluid-handling system should be sized. Students use this tool to check textbook numbers, engineers use it to size pipe and pump systems, and brewers or aquarium keepers use it to reason about flow and mixing. This page reports dynamic viscosity in pascal-seconds and the equivalent centipoise, plus kinematic viscosity in centistokes and m²/s, so the result drops straight into both CGS and SI fluid equations. Temperature is the variable that matters most here: a 20°C reading and an 80°C reading differ by more than a factor of three, so entering the right temperature is the whole game. When your problem is framed from pressure and pipe size rather than temperature, the Poiseuille's law calculator works from the flow side of the same physics. The water viscosity calculator is built so that this single temperature entry covers the full liquid range, which keeps the tool fast to use while still matching reference viscosity tables closely.

The calculator models liquid water with the Vogel-Fulcher-Tammann (VFT) equation, an empirical fit that captures how viscosity falls with temperature: μ(T) = A · exp(B / (T − C)), evaluated in kelvin using A = 0.02939 mPa·s, B = 507.88 K, and C = 149.3 K. The entered temperature is first converted to kelvin, then the exponential is evaluated to give dynamic viscosity in millipascal-seconds (numerically equal to centipoise). To reach kinematic viscosity the tool divides by the water density at that temperature using a standard fifth-order density polynomial, then converts m²/s to centistokes by multiplying by 1,000,000.

Worked example: at 20°C (293.15 K) the exponent is 507.88 / (293.15 − 149.3) = 3.530, so μ ≈ 0.02939 · e^3.530 ≈ 1.0035 mPa·s (1.0035 cP), and with water density near 998.2 kg/m³ the kinematic viscosity is about 1.0052 cSt, or 1.0052 × 10⁻₆ m²/s. Wikipedia's viscosity article lists water at 20°C at roughly 1.002 mPa·s dynamic and 1.004 cSt kinematic, values this model reproduces closely. For converting between the centipoise and centistokes units themselves, the Poise Stokes converter keeps the unit arithmetic separate from the temperature model, while the Reynolds number calculator is the natural next step once you have a cSt value, because kinematic viscosity drives that dimensionless number.

A second worked example at a hot extreme is worth seeing. At 80°C (353.15 K) the exponent is 507.88 / (353.15 − 149.3) = 2.524, so μ ≈ 0.02939 · e^2.524 ≈ 0.354 mPa·s (0.354 cP). Water density has dropped to about 971.8 kg/m³, giving a kinematic viscosity near 0.365 cSt, or 0.365 × 10⁻₆ m²/s. Comparing the 20°C and 80°C results shows the dynamic viscosity falling by a factor close to three over that 60-degree span, which is the practical reason pipe and pump designs almost always quote a temperature with the viscosity value.

Four terms show up whenever water viscosity is discussed, and keeping them straight prevents the most common unit mistakes:

The jump between the two viscosity families is the part worth internalising: at 20°C water's dynamic viscosity is about 1 cP and its kinematic viscosity is about 1 cSt, which looks like a coincidence but is really the consequence of water's density sitting near 1000 kg/m³. Pick a denser fluid and the two numbers diverge sharply. Kinematic viscosity divides dynamic viscosity by density, so the Water Density Calculator explains the temperature-dependent density term used here. According to the NIST reference tables, water viscosity is treated as a calibrated property of pure liquid water, which is why the purity and phase limits below matter.

Using the tool takes a few steps:

For example, a brewer chilling wort to 20°C reads 1.0035 cP dynamic and 1.0052 cSt kinematic; using 1.004 cSt in a Reynolds-number estimate confirms the transfer line stays laminar.

The calculator earns its place in a workflow because it:

• Replaces a printed viscosity table with an exact number at any temperature you type, not just the listed grid points.
• Returns both dynamic and kinematic forms, so you do not hand-divide by density before using a flow formula.
• Accepts °C, °F, and K entry, removing a separate unit-conversion step.
• Gives SI and CGS units together, matching both textbook problems and instrument readouts.
• Grounds the answer in a cited VFT model and density polynomial, so results are defensible in reports.

From there, the Water Pressure at Depth Calculator lets a viscosity value feed the next calculation, such as estimating the pressure a column of moving water exerts, without re-entering the temperature data.

Several inputs change the number the calculator reports:

A few limits are worth stating plainly. The VFT fit is empirical and is tuned to the pure-liquid range, so it should not be used below 0°C (supercooled water departs from the trend) or above 100°C at 1 atm (water is no longer liquid). It assumes fresh, pure water; saline or chemically treated water will differ, and those differences grow with concentration. The model also holds pressure at one atmosphere, so high-pressure process streams need a different correlation. These bounds are why the input clamps temperature to 0–100°C and why any value outside that window is rejected rather than extrapolated.

As noted by Omni Calculator's water viscosity tool, the sharp drop with temperature is the headline behaviour to design around. Because pressure and viscosity together shape convective heat transfer, the Prandtl number calculator builds on the same water properties this page reports.