Calculating pressure of supercritical water

[Decimator]

How would I go about calculating the pressure of supercritical water at an arbitrary temperature in a closed container?

 

[voko]

There is an international organization dedicated to the properties of water and steam, and they have published formulations that you can use to compute things very accurately. An example can be found here: http://twt.mpei.ac.ru/mcs/worksheets/iapws/IAPWS95.xmcd

 

[Chestermiller]

You can also use an appropriate equation of state for water, or a generalized corresponding states plot of compressibility factor z as a function of reduced temperature, reduced pressure, and acentric factor for water.