This shelf is rated on the box as 750lb capacity at failure. Given it's construction, I don't see how anyone could even aproach this number. My wife got this unit from Home depot, where it is also advertised as ~1700lb. I would be surprised if you could get 40lb on one of these shelves. They buckle and bow with nearly any load. Might work for TP or tissue box storage. Do a model number search, you will see it with two different ratings, both way off what it really is.