In general, load-bearing blocks must be able to withstand 2,500 to 3,000 psi (pounds per square inch) upon manufacture. However, since concrete blocks come in a range of sizes and shapes, their load-bearing capacity varies, therefore builders should test each specific type of block they plan to use.
Though the American Society for Testing and Materials provides guidelines, determining the exact load-bearing capacity of a cinder block is impossible without context. Not only do the sizes and shapes of blocks vary, but their chemical composition does too. Structural factors also affect how much weight a block can hold. For instance, a group of blocks can support more weight than those used individually, as the pressure is distributed over the network.