The article presents a mathematical model for calculating the characteristics of stability against overturning for mobile transport and technological machines equipped with boom lift manipulators. This model allows us to perform a quantitative assessment of the degree of influence of anchoring of outriggers on the increase of cargo stability of mobile machines during loading and unloading operations. The mathematical model is universal: it allows to estimate efficiency of additional anchoring irrespective of a design of outriggers and placement of anchor devices. On the example of several types of mobile machines shows the effectiveness of outriggers with built-in anchor devices on the basis of piercing working elements. The quantitative analysis of the impact of anchoring on the increase in the weight of the transported cargo and the maximum departure of the handling system and the reducing the width of the support contour of the mobile machine was performed. The analysis of the influence of anchoring on the increase of the maximum allowed angle of inclination of the support surface on which the mobile machine can be operated under the condition of stability against overturning was performed. These positive effects of additional anchoring of outriggers are important in the operations of special mobile machines, in the operations of loading and unloading operations in extreme conditions or during rescue operations in the aftermath of natural and man-made accidents and catastrophes. The formulas for linear two-factor approximation of the main characteristics of cargo stability against overturning of mobile machines depending on the angle of inclination to the horizon of the support countour and the degree of anchoring of outriggers was proposed. The accuracy of the approximation is maximum within 10%. The proposed recommendations for the rational choice of approximation points can significantly improve its accuracy for specific operating conditions of mobile transport and technological machines.