Water Viscosity Calculator
Estimate pure water's dynamic viscosity, kinematic viscosity, and liquid density from temperature, with instant unit conversion and a downloadable Excel workbook.
Temperature input
Below 100 °C, the calculator interpolates a verified water-property table. Above 100 °C, it treats the state as saturated liquid water and applies IAPWS-based density and viscosity correlations. Pressure and dissolved substances are not user inputs.
Live results
Dynamic viscosity near the selected temperature
The line compares the selected state with nearby temperatures in the same units, making the local temperature sensitivity easier to see.
Nearby water-property values
| Temperature (°C) | Dynamic viscosity (mPa·s) | Kinematic viscosity (mm²/s) | Density (g/cm³) |
|---|---|---|---|
| 0.00 | 1.7880 | 1.7890 | 0.9999 |
| 10.00 | 1.3059 | 1.3063 | 0.9997 |
| 20.00 | 1.0016 | 1.0034 | 0.9982 |
| 30.00 | 0.7972 | 0.8007 | 0.9956 |
| 40.00 | 0.6527 | 0.6579 | 0.9922 |
Rows are calculated from the same canonical model used by the result cards, chart, and Excel workbook. Values above 100 °C represent saturated liquid water, so actual system pressure must be high enough to keep water liquid.
How to use the Water Viscosity Calculator
What this calculator does. It estimates three temperature-dependent properties of pure liquid water: dynamic viscosity, kinematic viscosity, and density. Dynamic viscosity describes resistance to shear or flow; kinematic viscosity divides that resistance by density. The tool is useful for preliminary pipe-flow calculations, pump and heat-transfer estimates, laboratory planning, and checking how a temperature change may alter fluid behavior. It does not determine the properties of seawater, sugar solutions, glycol mixtures, contaminated water, ice, or steam, and it does not replace a pressure-specific property package near the critical point.
When to use it. Use the calculator when selecting an approximate viscosity for a Reynolds-number calculation, comparing cold and warm water in a hydraulic system, preparing a quick engineering estimate, or creating a documented property table for a calculation workbook. The underlying viscosity relationship follows the scientific framework described in the IAPWS formulation for the viscosity of ordinary water.
How to calculate. The calculator opens with a complete demonstration at 20 °C, and Download Excel is already available for that example. Follow these steps:
- Replace Water temperature with the value you need. Enter a plain decimal number using a period, such as
78or25.5. Commas, scientific notation, and mixed unit text are rejected to avoid ambiguous parsing. - Choose Temperature unit. The available choices are Celsius, Fahrenheit, and Kelvin. Changing the selection converts the current value, so 20 °C becomes 68 °F rather than being reinterpreted as 20 °F.
- Read the live result cards, chart, and nearby-property table. Then select Download Excel to create a current-state OOXML workbook. Select Reset to clear the demonstration data; this also clears results and can disable the export until a complete valid temperature is entered again.
Input guide. Water temperature is required and accepts one finite decimal value. After conversion, it must fall from 0 to 370 °C. For example, 68 °F, 20 °C, and 293.15 K represent the same state. A higher temperature generally lowers liquid-water viscosity; the common mistake is entering a value above the boiling point without considering the pressure needed to maintain a liquid phase. Temperature unit is also required because it controls conversion and display, but the canonical calculation always uses degrees Celsius internally.
Output guide. Dynamic viscosity (η) is shown in mPa·s, numerically equal to centipoise. It is the primary estimate and decreases strongly as water warms. Kinematic viscosity (ν) is shown in mm²/s, numerically equal to centistokes, and is calculated from dynamic viscosity and density. Liquid density (ρ) is shown in g/cm³. Model basis tells you whether the value came from table interpolation or from the high-temperature IAPWS-based correlation. Viscosity ratio vs 20 °C is an exact comparison to the 20 °C baseline: 1.0000× means equal, less than 1 means less viscous, and greater than 1 means more viscous. The header pills repeat the selected temperature, primary viscosity, and percentage change. In the table, each row contains Temperature, Dynamic viscosity, Kinematic viscosity, and Density; the highlighted row is the selected state. The chart's line series is Dynamic viscosity, and its highlighted point is the selected temperature.
Worked example. At the startup value of 20 °C, the interpolated property table gives dynamic viscosity of 1.0016 mPa·s and density of 0.9982 g/cm³. Kinematic viscosity is approximately η/ρ, so 1.0016 ÷ 0.9982 = 1.0034 mm²/s after rounding. The viscosity ratio is 1.0016 ÷ 1.0016 = 1.0000×, and the change from the 20 °C baseline is 0.00%. These same typed values appear in the first-open result cards, table, chart selection, and workbook checkpoints.
Learn more. For the thermodynamic assumptions behind liquid and saturated-water density, consult the IAPWS industrial formulation for water and steam properties. For measured low-temperature viscosity data, the NIST reference-data review of liquid-water viscosity provides experimental context.
How the calculation works
From 0 to 100 °C, the model linearly interpolates separate tabulated values for dynamic viscosity, kinematic viscosity, and density. Interpolating the three reported properties independently preserves the table's published rounding behavior at its anchor temperatures. From above 100 °C through 370 °C, the calculator estimates saturated-liquid density with an IAPWS saturation correlation and evaluates the IAPWS 2008 viscosity relationship without a near-critical enhancement term. Kinematic viscosity is then calculated as dynamic viscosity divided by density using compatible metric units.
When η is in mPa·s and ρ is in g/cm³, ν is numerically obtained in mm²/s.
Interpretation and limitations
Temperature is usually the dominant input for pure water at ordinary engineering conditions. Cold water can be several times more viscous than warm water, which changes Reynolds number, pressure loss, pump duty, and mixing behavior. Density changes more gradually at moderate temperatures but falls sharply as saturated liquid approaches the critical region. At temperatures above 100 °C, the phrase “liquid water” implies elevated pressure; at 1 atmosphere, water would instead boil. Near 374 °C, property gradients become steep and the simplified no-enhancement viscosity estimate should be treated as preliminary. The IAPWS supplementary release for liquid water near 0.1 MPa is a useful source for common-condition calculations.
For design work, confirm the actual pressure, composition, and temperature range. Dissolved salts, suspended solids, sugar, antifreeze, and other additives can materially change both density and viscosity. Also keep unit systems consistent: mPa·s equals cP, while mm²/s equals cSt, but neither is interchangeable with the other without density.