A typical eggshell takes a little more than 5.5 pounds of force to crack. A 30-pound cement block can be supported by eight eggs spread out over the block, still in cardboard egg containers. The raw calculation of 30 pounds divided by eight yields 3.75 pounds of force.
The key to egg cracking depends upon where the forces come from. Upright eggs, with the narrow end up, are able to distribute weight better than eggs on their side. Eggs crack easier when forces are applied at the widest part in the middle as opposed to either end. It is possible to walk on a dozen eggs in the carton, without cracking any of them, as long as the weight of each foot is evenly distributed.