Liquid water at near-atmospheric pressure
Find properties for flow, pumping, and heat-transfer calculations. Steam, boiling mixtures, and pressurized hot-water states need a separate reference.
Close to boiling at the reference pressure. Confirm actual system absolute pressure and local vapor pressure before assessing cavitation or liquid-only flow.
Properties at your temperature
Density, ρ
Mass per volume. Use for liquid pressure-drop and pump calculations.
Dynamic viscosity, μ
Resistance to shear. 1 cP = 1 mPa·s = 0.001 Pa·s.
Kinematic viscosity, ν
Dynamic viscosity divided by density. 1 cSt = 1 mm²/s.
Specific heat capacity, cp
Constant-pressure sensible heat capacity. Excludes phase change.
Thermal conductivity, k
Heat conduction property of the water itself, not a film coefficient.
Vapor pressure, pv
Liquid–vapor saturation pressure at this temperature; always absolute.
Prandtl number, Pr
Dimensionless momentum-to-thermal diffusivity ratio.
Thermal diffusivity, α
Thermal conductivity divided by volumetric heat capacity.
Quick reference table
SI values at 100 kPa absolute. Values are rounded; the lookup evaluates the correlations directly at your temperature.
| T (°C) | ρ (kg/m³) | μ (cP) | ν (cSt) | cp (kJ/kg·K) | k (W/m·K) | pv (kPa abs) | Pr |
|---|---|---|---|---|---|---|---|
| 0 | 999.84 | 1.7918 | 1.7921 | 4.2193 | 0.55565 | 0.6112 | 13.606 |
| 4 | 999.97 | 1.5673 | 1.5674 | 4.2074 | 0.56548 | 0.8135 | 11.662 |
| 10 | 999.7 | 1.3059 | 1.3063 | 4.1951 | 0.57879 | 1.2282 | 9.465 |
| 20 | 998.21 | 1.0016 | 1.0034 | 4.1842 | 0.598 | 2.3392 | 7.008 |
| 25 | 997.05 | 0.89 | 0.8926 | 4.1814 | 0.6065 | 3.1697 | 6.136 |
| 30 | 995.65 | 0.7972 | 0.8007 | 4.1799 | 0.61438 | 4.2467 | 5.424 |
| 40 | 992.22 | 0.6527 | 0.6579 | 4.1794 | 0.62848 | 7.3844 | 4.341 |
| 50 | 988.03 | 0.5465 | 0.5531 | 4.1812 | 0.64063 | 12.3513 | 3.567 |
| 60 | 983.2 | 0.466 | 0.474 | 4.1849 | 0.65102 | 19.9458 | 2.996 |
| 70 | 977.76 | 0.4035 | 0.4127 | 4.1901 | 0.65977 | 31.2006 | 2.563 |
| 80 | 971.79 | 0.354 | 0.3643 | 4.1969 | 0.66699 | 47.4147 | 2.228 |
| 90 | 965.31 | 0.3142 | 0.3255 | 4.2052 | 0.67278 | 70.1824 | 1.964 |
| 99 | 959.07 | 0.2846 | 0.2967 | 4.2144 | 0.67684 | 97.8518 | 1.772 |
Viscosity changes substantially with temperature
Using water properties in the calculators
- Pipe flow and friction: use density and dynamic viscosity at the flowing water temperature. If the calculator asks for kinematic viscosity, use ν instead.
- NPSH: use vapor pressure in absolute units at pump suction temperature. Enter the actual surface pressure separately. This page does not calculate available NPSH.
- Heat duty and heat exchangers: select cp at a representative bulk temperature for a modest temperature change. For larger changes, integrate cp over temperature or use an enthalpy difference from an appropriate property model.
- Convection: water conductivity k is not the surface film coefficient h. Use the temperature specified by your heat-transfer correlation, often bulk or film temperature.
Pr = cp μ / k
α = k / (ρ cp)
Use cp in J/(kg·K) in these relations.
Pipe pressure drop · Reynolds number · NPSH · Heat duty · Heat exchanger
Limits and common mistakes
The liquid properties use a fixed 100 kPa reference pressure. Standard atmosphere is 101.325 kPa; the two pressures are close but not identical. The boiling point at 100 kPa is approximately 99.61°C, so this page deliberately ends at 99°C.
Do not use this lookup for steam, ice, two-phase flow, seawater, glycol solutions, concentrated chemicals, or high-pressure water. Dissolved substances and pressure can change the properties. Water below its local boiling pressure will not remain a stable liquid at that temperature.
Density is mass density, not weight density. US viscosity units here use lbm, not lbf. Btu conversions use the International Table Btu. Copy buttons copy numbers only; match the selected unit in the destination calculator.
Sources and method
Density, cp, viscosity, and conductivity are calculated from IAPWS SR6-08(2011), Revised Supplementary Release on Properties of Liquid Water at 0.1 MPa: specific-volume equation (2), heat-capacity relation in Table 2, and transport equations (7) and (8). Attribution: International Association for the Properties of Water and Steam.
Vapor pressure uses IAPWS-IF97, Region 4, equation (30). Kinematic viscosity, Prandtl number, and thermal diffusivity are derived from the primary properties.
Displayed digits are for calculation convenience, not a claim of measurement accuracy. At stable liquid conditions the supplementary release gives approximate uncertainties of 0.0001% for density, 0.1% for cp, 1% for viscosity, and 1.5% for conductivity. Sources checked September 28, 2026.