Load capacity on shelving is quoted per shelf, not per unit, and that is the figure that matters. A five shelf unit rated at a figure per shelf carries five times that in total, but only if the weight is spread rather than concentrated on one level. Concentrating a heavy load on one shelf is the usual reason a unit fails rather than the total being exceeded.
Shelf count and footprint then decide how the storage actually works. A 4 shelf unit at 760 x 300 x 1520mm gives generous spacing for boxed goods. A 5 shelf unit in similar height gives closer spacing, which suits smaller items stacked no more than a few deep.
Modular racking takes the same idea and adds a working surface. Racking at 750mm, 1500mm and 1600mm is held in 2, 3 and 4 tier forms with hardwood, stainless steel and pegboard tops, so a run stores and works rather than only storing. Pegboard tops turn the back of a run into hanging storage rather than leaving it as a blank panel.
Specialist racks solve what a flat shelf cannot. A two level tyre rack at 200kg per level and 1950mm wide holds tyres on their edge with extensions to lengthen the run, and a spanner rack holds tools in order. Send the stock and weights to 07754288583 on WhatsApp. Shelving panel supports reinforce a shelf carrying a point load rather than a spread one.