Regularities of the effect of strength and ductility of steel ($\sigma_{0.2}$ = 140…2100 MPа, $\psi_{\textrm{K}}$ = 3…83%) on degree of embrittlement of prismatic pre-cracked specimens in three-point bending is analysed. Instead of plasticity ($\psi_{\textrm{K}}$), it is proposed to analyse the characteristic of deformation resistance (break resistance), $B_{r}$ = $S_{\textrm{K}}$/$\sigma_{0.2}$ which is responsible for the resistance of steel to brittleness in inhomogeneous fields created by stress raisers (SR—notches, cracks). As shown, in this type of test the criterion value of brittle fracture of steels at a temperature of 293 K can be a critical value of the parameter of break resistance $B_{rc}$ = 1.65. Deviation $B_{r}/B_{rc}$ > 1 can be used as a measure of protection of steel from brittleness, while at $B_{r}/B_{rc} \leq$ 1 the ratio serves as a quantitative measure of the manifestation of brittleness of steel in bending pre-cracked specimens. The possibility of predicting the characteristic of embrittlement of steel $B_{r}/B_{rc}$ by the calculated method according to the basic mechanical characteristics $\sigma_{0.2}$, $\sigma_{B}$, $S_{\textrm{K}}$, which were obtained during tensile tests of standard specimens, is shown.