I have seen an excel sheet in calculator to calculate the size of transformer.
There are option to put the vales of Kw,PF,Qty and Equipment D.F.
I could not understand what is D.F.
What is the equation to calculate the D.F and equation to calculate the total load D.F?

D.F. is probably the Demand Factor.
What percentage of the transformer rating is being used.

DF= Demand Factor...a ratio portion of the total demand load of a system (or system part) expressed as a percentage calculated for usage allowed. [Art.220]

Note that including the overall Demand Load depends on using a standard or optional method load calculation as permitted in Art.220 for determining the transformer rated capacity size needed.