How to calculate Specular value for Principled BSDF node from IOR? With regard to the manual the Specular value for the new Principled BSDF node can be computed with following formula:

$\text{specular}=\left(\frac{\text{ior}-1}{\text{ior}+1}\right)^2/0.08$
For example:

water: ior = 1.33, specular = 0.25
glass: ior = 1.5, specular = 0.5
diamond: ior = 2.417, specular = 2.15


But I am getting other numbers. Is the formula wrong? If so, what is the correct one?
The formula above is correct. Just don't mistake square with square root as I did before.