Axeleratio
Calculator
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The following calculator is based on a JavaScript implementation of the Kell equation at axeleratio.com.
Enter the temperature in °C and press the button to get the density of water at atmospheric pressure:
Temperature/°C:
Density/(kg/m3):
Molar Vol./mL:
The Kell equation, employed by the calculator, is, in MathML mark-up [supported by Firefox and Safari]:

${\rho }_{{\text{H}}_{2}\text{O}}=\frac{\left(\left(\left(\left(aT+b\right)T+c\right)T+d\right)T+e\right)T+f}{1+gT}$
${\rho }_{{\text{H}}_{2}\text{O}}$ is the density of water in kg/m3. $T$ is the temperature in °C. The coefficients are $a=-2.8054253\cdot {10}^{-10}$, $b=1.0556302\cdot {10}^{-7}$, $c=-4.6170461\cdot {10}^{-5}$, $d=0.0079870401$, $e=16.945176$, $f=999.83952$ and $g=0.01687985$. A molar mass of ${M}_{{\text{H}}_{2}\text{O}}=18.0153$ g/mol is used to calculate the molar volume corresponding to the density value.

Do it right! Otherwise...
...you will be assisted by an explaining error code in the density field as a result of entering an unacceptable temperature value:

E0010: entered value below applicable temperature range.
E0019: entered value above applicable temperature range.
E0090: unacceptable temperature value.
E0111: unresolved failure during calculation.

Good to know:
Experimental density data for liquid water at atmospheric pressure are mostly available for the temperature range from 0 °C to 100 °C. But liquid water can exist at 1 atm from about -40 °C to above 300 °C. The applicable temperature range for the above calculator is -30 °C to 150 °C, the range over which Kell provides tabulated, calculated density values along with other volume properties of water at 1 atm (Table III in [1]). The Kell equation has been employed in modeling the density of aqueous electrolyte solutions [2].

Bibscope-enhanced References
 [1] Kell, G. S. Density, Thermal Expansivity, and Compressibility of Liquid Water from 0° to 150°C: Correlations and Tables for Atmospheric Pressure and Saturation Reviewed and Expressed on 1968 Temperature Scale J. Chem. Eng. Data, 1975, 20 (1), pp. 97-105. DOI: 10.1021/je60064a005. [2] Laliberté, M. and Cooper, W. E. Model for Calculating the Density of Aqueous Electrolyte Solutions J. Chem. Eng. Data, 2004, 49 (5), pp. 1141-1151. DOI: 10.1021/je0498659.