wt is related to specific gravity of the liquid which also is related to the temp at which it is measured.
specific gravity is a dimensionless measurement which is defined as the ratio of density of the material to the density of water at a specified temperature.
specific gravity is often expressed as:
SG = ρ / ρH2O
SG = specific gravity
ρ = density of fluid
ρH2O = density of water
it's common to use the density of water at 4 deg C as a reference. this is the temp at which the density of water is at the highest.
therefore, wt varies slightly depending upon type of alchohol & temp conditions.
w/o going into more precise detail, which prob. isn't necessary for your purposes, figure, roughly, alcohol weighs ~80% of what a similar volume of water weighs.
since we're talking of "rough", or approximate, values this applies to both ethyl alcohol & denatured alcohol.