2- Using mass of the film, m according to the next details::
W1 is the weight of cleaned substrate
W2 is the weight of cleaned substrate plus film
W2-W1= the weight of the film
ΔW=mg
m = ΔW/g
m=ρ.V ; ρ, is the density of film material and V is the volume of the film
the Volume = (Width X Length X Thickness) of the film
3- An interferometric method, more details is available at: TOLANSKY S. Multiple beam interferometry of surfaces and films. London: Oxford University Press, 1988: 147.