Water Viscosity Calculator
Get water's viscosity at any temperature from 0 to 100 °C (32 to 212 °F). Enter the temperature in °C or °F and read the dynamic viscosity in mPa·s (identical to centipoise), the kinematic viscosity in m²/s and cSt, and the density used to convert between them.
Example: with Water temperature 20 · Temperature unit °C → Dynamic viscosity μ: 1.002 mPa·s (= cP).
- Kinematic viscosity ν = μ/ρ1.004 × 10⁻⁶ m²/s (1.004 cSt)
- Density ρ998.2 kg/m³ (specific gravity 0.9982)
Computed by the calculator below using its default values. Change any input to see your own numbers.
μ = 2.414×10⁻⁵ × 10^(247.8/(T−140)) Pa·s with T in kelvin — the Vogel-type correlation accurate to about ±2.5% for liquid water. At 20°C it gives 1.002 mPa·s.
Why warm water flows so much easier
Viscosity is a liquid's internal friction, and in water it is set by hydrogen bonds constantly forming and breaking between molecules. Heat speeds up the breaking, so viscosity collapses as temperature rises — from 1.75 mPa·s near freezing to 1.00 at 20°C to 0.28 at boiling, a six-fold drop. No simple linear rule survives that curve; this tool uses the Vogel-type exponential correlation μ = 2.414×10⁻⁵ × 10^(247.8/(T−140)), which tracks published data within about ±2.5% across the liquid range.
The handy anchor: at 20°C water is almost exactly 1 centipoise. That is not a coincidence — the centipoise was effectively scaled around water at room temperature.
Dynamic vs. kinematic — pick the right one
Dynamic viscosity μ (mPa·s or cP) measures the shear stress needed to slide layers past each other; it is what pumps fight. Kinematic viscosity ν = μ/ρ (m²/s or cSt) folds in density and governs how flows behave under their own inertia — it is the property in the Reynolds number, Re = vL/ν, that decides laminar versus turbulent flow. Because water's density only drops about 4% from 0 to 100°C while μ drops 84%, the two track each other closely for water, but the distinction matters the moment you compare against oils or gases.
How it’s calculated
Dynamic viscosity: μ = 2.414×10⁻⁵ × 10^(247.8/(T−140)) Pa·s, T in kelvin (Vogel-type correlation, ±2.5% for liquid water; e.g., Al-Shemmeri, Engineering Fluid Mechanics) — reported ×1,000 as mPa·s = cP. Density: ρ = 1000×(1 − (t+288.9414)/(508,929.2×(t+68.12963))×(t−3.9863)²) kg/m³, t in °C (McCutcheon et al. 1993, ±0.02%). Kinematic: ν = μ/ρ. °F converted as (°F−32)×5/9.
Pure water at atmospheric pressure — dissolved salts and pressure raise viscosity (seawater runs roughly 8% higher), and the correlation is not valid for ice or steam.
Water viscosity and density vs. temperature
| Temp (°C) | μ (mPa·s) | ρ (kg/m³) |
|---|---|---|
| 0 | 1.75 | 999.9 |
| 10 | 1.30 | 999.7 |
| 20 | 1.00 | 998.2 |
| 30 | 0.80 | 995.7 |
| 50 | 0.54 | 988.1 |
| 75 | 0.37 | 974.8 |
| 100 | 0.28 | 958.1 |
Computed with the Vogel and McCutcheon correlations stated above; matches CRC/IAPWS tabulated values within ~2%.
Common mistakes
- Mixing up mPa·s and Pa·s — water at 20°C is 1.002 mPa·s, i.e., 0.001002 Pa·s; a 1,000× slip is the classic error.
- Using cP where a formula wants cSt (or vice versa): they only coincide when density is exactly 1 g/mL, which is nearly — not exactly — true for cold water.
- Extrapolating the correlation below 0°C or above 100°C, where liquid water at 1 atm doesn't exist.
- Applying pure-water values to brines, wastewater, or sugar solutions — dissolved solids raise viscosity substantially.
Frequently asked questions
What formula does this calculator use?
The Vogel-type correlation μ = 2.414×10⁻⁵ × 10^(247.8/(T−140)) Pa·s with T in kelvin, accurate to about ±2.5% for liquid water, plus the McCutcheon polynomial for density so it can also report kinematic viscosity ν = μ/ρ.
What is the viscosity of water at room temperature?
About 1.00 mPa·s (1 centipoise) at 20°C and 0.89 mPa·s at 25°C. That 11% drop over five degrees shows how steep the temperature dependence is.
What's the difference between dynamic and kinematic viscosity?
Dynamic (μ, in mPa·s or cP) is resistance to shear; kinematic (ν = μ/ρ, in m²/s or cSt) divides by density and is what the Reynolds number uses. For water at 20°C: μ = 1.002 cP, ν = 1.004 cSt.
Does pressure change water's viscosity?
Barely, for ordinary conditions — a few percent up to hundreds of atmospheres. Temperature is the lever that matters, which is why this tool only asks for temperature.
Is honey really thousands of times more viscous than water?
Yes — typical honey runs 2,000–10,000 mPa·s versus water's 1. Motor oil (SAE 30) sits near 200 mPa·s at room temperature. Water is the 1.0 benchmark the cP scale was built around.