In the arena of commercial fans (such as those used in homemade wind tunnels), the pressure-drop across the fan is measured in units of "inches of water", and "cfm", neither of which appear to be supported by Google Calculator. I would appreciate the addition of the two units. Their conversion to the MKS system is shown below:
The appropriate google query string (included in case you wish to
recompute with more precise values of the constants employed) to
compute the number of pascals in one inch of water is:
.0254 m * 1 m^2 * (1000kg / m^3) * 9.81 m / s^2 / 1 m^2
where .0254 is the number of meters in one inch, 1000kg/m^3 is the density of water, and 9.81 is the magnitude of the gravitational acceleration at sea level. The resulting value is 249.17400 pascals / inch of water.