Please in the attached, I will like to know how to calculate W AND N.

thanks.

You don't calculate these values, you read them from a stadard or a drawing.

thanks for your quick reply moverz,

I will like to know which standard and how.

Best Regards.

If you are designing a special flange, you determine the dimensions. If it's a standard flange then you should refer to ASME B16.5 or B16.47A/B, or maybe a DIN code. There are several other codes too.

If you don't know where to find this data you probably should not be trying to use it.