Mr. Khattab,

If you have not vibrational resolved transitions, you cannot account for the FWHM, generally. 

We normally choose FWHM of band in theoretical uv-vis spectrum according to experimental band shape so that one can compare both theoretical and experimental UV-Vis bands . 

Thanks Bojidarka. I need to read more about vibrationally resolved absorption and emission spectra.

@Mohammad. Could you explain in details. how to make consistent comparison, however theoretical spectrum gives me osc. strength and/or e on y-axis (not absorbance)

You may convert your experimental data (y-axis) in epsilon as Absorbance = ebc.

As the limiting condition for Beer-Lambert Law is A(λ) < 1.0. Therefore, choose the concentration of solution such that the absorbance be less than one. 

Important information:

http://www.lasalle.edu/~gentry/C332/Lab.%20Oscillator%20Strengths.pdf

http://www.gaussian.com/g_whitepap/tn_uvvisplot.htm