This link Grout Cell Calculations provides the individual grout cell information (cubic inches, cubic feet, and cubic yards) for each type of block that should enable masons to accurately determine the amount of grout that will be required on a project and therefore more accurately bid the project.
The individual wall thicknesses of Omni Block units are 1.25″ whereas many of the standard CMU thicknesses are 1.50″. The calculations presented here are based on this assumption, making the cells of the 8″ and 12″ standard CMU slightly smaller than the Omni Block corner and jamb block cells. Many block plants have switched to the newer 1.25″ wall thickness which would make the Omni Block units and the standard CMU almost identical.
The Omni Block stretcher cells of the 8″ and 12″ units are identical. The 12″ Omni Block stretcher cell is about 67% less than the 12″ standard cells, while the 8″ Omni Block stretcher cell is about 40% less than the 8″ standard cells. The drawings included in the calculations provide these details.