In silico PCR: any models that can quantitatively predict the initial content from the end amplified result?
The basic equation for PCR kinetics (Equation 1) states that the amount of amplicon after c cycles (Nc) is the starting concentration of the amplicon (N0) times the amplification efficiency (E) to the power c. The PCR efficiency in this equation is a number between 1 and 2 (2 indicates 100% efficiency).  NCBI 

In this  article  on research gate they said  amplifx  was the software you were looking for to, calculate "(i.e. expected efficiency in PCR reaction)". The amplifx even mentions "Testing primers in in silico PCR".