Tensorial-type failure criteria with linear and quadratic terms are used to calculate the strength of paperboard under plane stress. Theoretical predictions and experimental data are correlated in all four quadrants of biaxial normal stress with various levels of shear. Several methods are examined for determining the interaction coefficientF12. Comparisons are made with optimum values obtained from least-squares analyses. The best analytical-experimental agreement at all levels of shear is obtained approximately by using coefficientF12 equal to zero. The sensitivity ofF12 to errors in experimental input data is also studied. Reliable correlation with experiment, as well as operational simplicity, make these criteria attractive for predicting the strength of paperboard.