Stacking multiple magnets together can make them stronger. Two or more magnets stacked together will exhibit nearly the same strength as a single magnet of the combined size.
For example, if you stacked two 1/2 x 1/4 inch thick disc magnets to make a 1/2 x 1/2 inch combined size, the two magnets would have nearly same strength as a single 1/2 x 1/2 inch magnet.
Does that mean the strength is doubled?
We are often asked if stacking two magnets together will double the pull force and the answer to that is not always. In the example below, you can see how the pull force increases and eventually begins to level off as you continue to double the thickness.