Yield-density equations are not well explored in additive intercrops. A modification of the standard asymptotic yield-density equation for application to additive intercrops was proposed, and in turn, derived equations were found. With wheat (Triticum aestivum L.)/faba bean (bean; Vicia faba L.) intercropping systems, as an example, the equations were applied to quantify seed yields in three field experiments. Although, the standard asymptotic yield-density equation quantified each of the sole crop and the intercrop yields of the major component (wheat) well for all the three experiments, the modified version worked well in only one of the experiments. Even though the response of the minor component (bean) was not consistent across the experiments, in one of the experiments, in addition to using modified standard yield-density equation to quantify the total intercrop (wheat + bean) yield (plus sole crop of the minor component; bean), the wheat intercrop and bean intercrop yield were quantified simultaneously using the equations proposed here. In conclusion, for a standard additive intercrop, the proposed yield-density equations can quantify the yields well and should be adopted by others using similar design.