Dynamic Viscosity of Water at 20 °C
| Value | 0.001002 Pa·s |
| Status | Measured: ± 0.000005 Pa·s (0.005 relative) |
| Source | IAPWS / CRC Handbook of Chemistry and Physics, 104th ed. |
| Categories | Material PropertiesEngineering & TradeFluid Properties |
| micropascal second | 1,002 μPa·s |
| millipoise | 10.02 mP |
| pound per foot hour | 2.4239265 lb/(ft·h) |
| millipascal second | 1.002 mPa·s |
| centipoise | 1.002 cP |
| microreyn | 0.14532781 μreyn |
| poise | 0.01002 P |
| pascal second | 0.001002 Pa·s |
| pound per foot second | 0.00067331291 lb/(ft·s) |
| pound-force second per square foot | 0.000020927205 lbf·s/ft² |
| kilopascal second | 0.000001002 kPa·s |
| reyn | 1.4532781e-07 reyn |
Water at any temperature
0 to 100 °CThe value above is one point on this curve. Liquid water from 0 to 100 °C at 1 atm — density, viscosity, specific heat, thermal conductivity and vapour pressure, all at the same state.
Learning zone
Water at 20 °C is very nearly exactly 1 centipoise, which is not a coincidence: the poise scale was set up so that water would land there. The kinematic viscosity is 1.004 × 10⁻⁶ m²/s, or 1.004 centistokes. Both feed the Reynolds number, and therefore every friction factor, settling velocity and pump-suction calculation you will do with water.
Temperature dominates, and by more than most people expect. Water at 5 °C is 1.52 mPa·s and at 80 °C only 0.355 — a factor of four across ordinary building temperatures. Since Re scales as 1/µ, a chilled-water line and a heating line at the same velocity are at very different Reynolds numbers, and laminar-regime behaviour in cold, small-bore or glycol-laden lines is far more common than designers assume. Pressure barely matters for liquids. Add 50 % propylene glycol and viscosity at 0 °C rises to roughly 15 mPa·s, at which point coil film coefficients collapse and pump curves stop matching the catalogue.