What is so ironic about this question is it may be the most asked one across the consumer base of metal detectors. Yet, it can’t even be answered straight up. This question is like a math equation that is filled with several different variables. In other words, there are too many factors that come into play to provide a direct answer to this question. For example, the length of time an object rests underground can have serious implications on if the detector can actually detect it. This is because, after a while, the metal will corrode due to the soil.
Also, the size of an object can play a role. If it is smaller, it will be more difficult for the machine to detect the piece of metal. Finally, the conductive properties of the soil (if it is heavily mineralized) can reduce the penetration power.