Water Viscosity Calculator — Dynamic & Kinematic Viscosity of Water at Any Temperature

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 — maple syrup, a very viscous fluid, pours much slower than milk because milk's viscosity is far lower. We can also express viscosity as the internal friction of a fluid in motion: the attraction between molecules of a viscous fluid is much higher than that of a less viscous fluid.

When heat or additional thermal energy is applied to a liquid, its molecules start moving faster and their mutual attraction weakens. As a result, liquid molecules move more freely and the viscosity decreases with rising temperature.

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 (20 °C / 68 °F) is approximately 1.002 mPa·s (millipascal-seconds), which is equivalent to 1.002 cP (centipoise). As temperature increases, this value decreases significantly — water at 100 °C (212 °F) has a dynamic viscosity of only about 0.282 mPa·s.

Dynamic vs. Kinematic Viscosity

Dynamic viscosity (also called absolute viscosity) tells us about the force required to move a fluid at a certain speed. It is measured in:

• Metric: mPa·s (millipascal-seconds) or the equivalent cP (centipoise)
• American (Imperial): lbf·s/ft² (pound-force second per square foot)

Kinematic viscosity tells us about the speed a fluid reaches when a particular force is applied. It equals the dynamic viscosity divided by the fluid's density:

ν = μ / ρ

It is measured in:

• Metric: mm²/s or the equivalent cSt (centistokes)
• American (Imperial): ft²/s (square feet per second)

How to Use Our Water Viscosity Calculator

1. Select your preferred unit system — Metric (°C) or American/Imperial (°F).
2. Enter the water temperature in the selected unit. Valid range: 0 °C–370 °C (32 °F–698 °F).
3. Click Calculate. The calculator will instantly display:
   • Dynamic viscosity in mPa·s (= cP) and lbf·s/ft²
   • Kinematic viscosity in mm²/s (= cSt) and ft²/s
   • Water density at the given temperature
   • Applied formula with computed values

How to Calculate the Viscosity of Water

This calculator uses the Andrade / ASTM D341 equation, which is one of the most reliable empirical formulas for water viscosity across a wide temperature range:

μ = 0.02414 × 10^{(247.8 / (T_K − 140))}

Where:

• μ — dynamic viscosity in mPa·s (centipoise)
• T_K — temperature in Kelvin (T_K = T°C + 273.15)

This formula is valid for temperatures from 0 °C to approximately 370 °C (covering both liquid water and near-critical conditions).

How to Calculate the Kinematic Viscosity of Water

Once you have the dynamic viscosity μ and the water density ρ (in kg/m³), the kinematic viscosity is:

ν (mm²/s) = μ (mPa·s) / ρ (kg/m³) × 1000

The density of water changes with temperature — it peaks near 4 °C (≈ 999.97 kg/m³) and decreases both above and below that temperature.

Effect of Temperature on Water Viscosity

Viscosity of Water in Different Units

Engineers and scientists often need to convert viscosity to different unit systems. Here are the most common conversions:

• 1 mPa·s = 1 cP (centipoise)
• 1 mPa·s = 2.0885 × 10⁻⁵ lbf·s/ft² (pound-force second per square foot)
• 1 mPa·s = 6.7197 × 10⁻⁴ lb/(ft·s) (pound per foot-second)
• 1 mm²/s = 1 cSt (centistokes)
• 1 mm²/s = 1.07639 × 10⁻⁵ ft²/s (square feet per second)

FAQs

What is the viscosity of water at room temperature?

At 20 °C (68 °F), the dynamic viscosity of water is approximately 1.002 mPa·s (1.002 cP) and the kinematic viscosity is approximately 1.004 mm²/s (1.004 cSt).

Does water viscosity increase or decrease with temperature?

Water viscosity decreases as temperature increases. Hot water flows more easily than cold water because higher thermal energy weakens the intermolecular bonds that resist flow.

What is the unit of dynamic viscosity?

In the SI (metric) system, dynamic viscosity is measured in Pascal-seconds (Pa·s) or the practical unit millipascal-seconds (mPa·s), also called centipoise (cP). In the American (Imperial) system, it is expressed in lbf·s/ft² or lb/(ft·s).

What is the difference between dynamic and kinematic viscosity?

Dynamic viscosity measures the internal resistance of a fluid to shear stress (force per unit area). Kinematic viscosity equals dynamic viscosity divided by fluid density — it reflects how quickly a fluid flows under gravity. For water at 20 °C, both values are approximately 1.0 in their respective common units (mPa·s and mm²/s).

Can I calculate viscosity above 100 °C?

Yes! This calculator supports temperatures up to 370 °C (698 °F). Note that above 100 °C at standard atmospheric pressure, water would be steam — but at elevated pressures (e.g., inside industrial boilers), water remains liquid up to its critical point at approximately 374 °C.