Water Viscosity Calculator
This water viscosity calculator will help you determine the viscosity of water at room temperature, or at any temperature, even those above 300 °C! In this calculator, you will learn what the absolute viscosity of water is (commonly known as the dynamic viscosity of water) and learn how to convert it to kinematic viscosity. You will also find out how to calculate the viscosity of water and the effect of temperature on the viscosity of water using a variety of methods.
This water viscosity calculator provides you with a water viscosity to temperature chart and table so you can reference the effects that temperature has on water's viscosity and density of water. Although our charts and tables are in SI units, in this calculator, you will also learn how we can express the viscosity of water in English units. Keep on reading to learn more!
What is viscosity?
Viscosity is the measure of a fluid's resistance to flow. The higher the viscosity of a fluid (liquid or gas), the slower it traverses across a surface. Imagine dripping maple syrup on your waffles for your breakfast. Maple syrup, a very viscous fluid, would pour slower than when you pour milk on your cereal as milk's viscosity is much lower. We can also express viscosity as the internal friction of a fluid in motion. The attraction between the molecules of a viscous fluid is much higher than that of a less viscous fluid.
However, when we apply heat or additional thermal energy to our fluids, their molecules start moving faster. As a result, in gases, molecules experience more friction against each other, making them flow slower and become viscous. In liquids, when molecules start to move faster, their attraction from each other weakens. This weakening results in liquid molecules to move more freely and, therefore, with a lower viscosity.
In this article, we'll focus more on the viscosity of liquids, specifically on the kinematic viscosity and the dynamic viscosity of water. When dealing with viscosities, when we mention "viscosity," we actually mean dynamic viscosity. Dynamic viscosity, or the absolute viscosity of water, or any fluid, is proportional to the tangential shear stress per unit area needed to move one plate at a constant speed over another plate at a maintained fluid thickness between these two plates, like in a Couette flow, as shown below:
The larger the force or stress needed to move the plate, the more viscous the fluid is. When choosing between the two viscosities, it is worth noting that dynamic viscosity tells us about the force required to move the fluid at a certain speed. On the other hand, the kinematic viscosity tells about the speed the fluid reaches when a particular force is applied to the fluid.
We can measure dynamic viscosity in millipascals-second (mPa⋅s) or with a fancier equivalent called the "centipoise." On the other hand, we can express kinematic viscosity in square millimeters per second (mm2/s), which also has an equivalent unit called "centistokes." For the simplicity of this text, we will only be using milliPascals-second and square millimeters per second for dynamic viscosity and kinematic viscosity, respectively.
However, if you need to express the viscosity of water in English units, you can always convert the milliPascal part to pound-force per square foot, and the square millimeters to square inches, for the dynamic viscosity and kinematic viscosity respectively. You can use our pressure converter and area converter for these procedures, especially if you have a lot of values to convert.
What is the viscosity of water?
Water, being the most studied liquid, is the best fluid to start with when learning about viscosity. The dynamic viscosity of water at room temperature has a value of around 1.0 mPa⋅s, and it decreases as temperature increases. This value is the viscosity of water at 20°C. Below is a water viscosity to temperature chart that shows the effect of temperature on the dynamic viscosity and kinematic viscosity of water.
The water viscosity to temperature chart above is a visual representation of the data recorded below. Experiments have been made at different temperatures to obtain this data. In the table below, we have also included water density since it has a crucial role in converting dynamic viscosity to kinematic viscosity, as you will see in the next section of this text.
How to use our water viscosity calculator?
To use our calculator, input the temperature that you want to know the water viscosities for. You can also mouse-over (for computers) or drag-over (for mobile phones) the chart in our calculator to see the viscosity values at any temperature.
We also included in our water viscosity calculator the water density values at any temperature as a bonus.
How to calculate the viscosity of water?
To determine the viscosity of water at any temperature, we can use the table or the water viscosity to temperature chart provided in the Effect of temperature on viscosity of water section of this text and use the interpolation method for other temperatures not written in the table. Using the chart, we can approximate the temperature we want, and then (1) draw a vertical line from the x-axis until it intersects the curve. By (2) drawing a horizontal line from this intersection, we can now see the approximate water viscosity at a particular temperature, like with the one shown below for 125°C:
Depending on the method you decide to choose (use the water viscosity calculator with interpolation method or draw lines), you can get the values for water viscosity (dynamic and kinematic). However, it is then a good practice to choose only one method when comparing multiple viscosity values at different temperatures. This way, the concepts behind the values you get will be consistent and appropriate for comparisons. Anyway, we'd choose the first method (the interpolation method) because it is more accurate than drawing vertical and horizontal lines over a chart.
How to calculate the kinematic viscosity of water?
Aside from calculating the dynamic viscosity of water, we may also need to determine the kinematic viscosity of water at any temperature. We can also use the water viscosity-temperature chart or table provided in this text and follow the same instructions given above. We can also calculate water's kinematic viscosity from dynamic viscosity by dividing the dynamic viscosity by water's density, as shown below:
νT = ηT / ρT
νTdenotes the kinematic viscosity at temperature T;
ηTis the dynamic viscosity at temperature T; and
ρTis the density of water at temperature T.
Please note that temperature also affects the density of water and that all necessary linear interpolation should be done prior to calculation. Let's say we have previously calculated the density of water at 78 °C to be approximately equal to
0.973 g/cm3 . Also, using the interpolation method, we find the dynamic viscosity of water at 78 °C to be around
0.36336 mPa⋅s. We then convert this value of dynamic viscosity to kinematic viscosity as follows:
ν78°C = η78°C / ρ78°C
ν78°C = 0.36336 mPa⋅s / 0.973 g/cm3
ν78°C = 0.3734429599 mm2/s ≈ 0.37344 mm2/s
Using the conversion method shown above, we can now say that water's kinematic viscosity at 78 °C is approximately 0.37344 mm2/s.