A video processing method is provided to include determining, for a current video block of a video, a final prediction block for the current video block by refining one or more initial predictions for the current video block using an optical flow calculation based on a gradient of initial prediction samples according to a precision rule; and performing a conversion between the current video block and a coded representation using the final prediction block, wherein the optical flow calculation includes a prediction refinement with optical flow (PROF) procedure or a bi-directional optical flow (BDOF) procedure, wherein the precision rule specifies to use a same precision for representing the gradient for both the PROF procedure and the BDOF procedure.