A formulation that readily allows quantitative comparisons with experimental chemical yields in long-range charge transfer in DNA is developed. The theory is based on a superexchange-mediated sequential hopping model that takes into account the multistep charge migrations (hopping) among guanine bases and the individual substep of superexchange (tunneling) through adenines and/or thymines. An exact Ohm's law is established for kinetic multistep hopping processes, while the scattering matrix technique is exploited to determine the coherent unistep contributions. Presented are also the quantitative comparisons with the experimental measurements in some DNA molecules involving intrastrand and/or interstrand charge transfer processes in aqueous solution. The dependence of product yield on both the length and the sequence of DNA is clearly demonstrated.