The take-off angle of the jet from aeration facilities is a critical hydraulic parameter for accurately calculating the aerated cavity length. The turbulent characteristics of the jet indirectly influence the take-off angle through modifying the diffusion angle, and the underlying physical mechanism is considerably complex. To rigorously account for the effect of flow turbulence on the diffusion angle, the turbulent diffusion angle at the lower jet nappe was quantified based on the theory of two-dimensional free turbulent jets, leading to the derivation of a modified formula for the take-off angle of jet from aeration facilities. A total of 193 test conditions were examined through laboratory experiments conducted in a precision tilting flume, together with engineering applications. The prototype cavity lengths predicted by six alternative take-off angle estimation methods were compared with measured prototype data. Both the model experiments and engineering validations confirm that the proposed correction method for the take-off angle of jet from aeration facilities is reasonable and reliable.