Research on liming sandy soils in Brazil has been ongoing for decades, since the 1980s sandy soils were first integrated into agricultural production and farmers have tended to apply limestone at rates higher than those suggested in standard recommendation manuals. The rates recommended by these manuals can achieve the target soil pH for optimal crop yields, but they often fail to meet the calcium (Ca) and magnesium (Mg) needs of plants, resulting in suboptimal or economically unprofitable yields. This study proposes an adjustment in the recommendation for lime requirements (LR) for sandy soils. Using a database (112 samples) of liming experiments carried out in Mato Grosso and Bahia Brazilian’s states, scatter plots were established relating the Ca2+ and Mg2+ contents (X) in the 0-20 and 20-40 cm layers and the relative yield (Y) of soybeans, for soils with up to 150 g kg-1 of clay (0-20 cm). Using the boundary line method, the XY pairs were identified at the upper limit of the dispersion of points and regression equations were established. The critical levels were estimated as being the Ca2+ and Mg2+ levels related to 100% relative production, in two soil layers: 0-20 cm (2.9 for Ca2+ and 0.9 cmolc dm-3 for Mg2+); 20-40 cm (0.9 for Ca2+ and 0.5 cmolc dm-3 for Mg2+). Considering that sandy soils have a higher bulk density (BD), the study suggests including soil density in the equation. The proposed formula for LR is a first approximation, designed to help optimize lime application for sandy soils: LR (t ha-1) = [1] + [2]; [1] 0-20 cm – LR (t ha-1) = {Al3+ + [3.8 - (teor Ca2++Mg2+)]} x BD; and [2] 20-40 cm – LR (t ha-1) = {Al3+ + [1.4 - (teor Ca2++ Mg2+)]} x BD.