How does a magnets strength drop off over distance?
The strength of a magnetic field drops off roughly exponentially over distance. Here is an example of how the field (measured in Gauss) drops off with distance for a Samarium Cobalt Grade 18 disc magnet which is 1″ in diameter and 1/2 ” long. Distance, x Field at Distance x 0.063 2,690 0.125 2,320 0.188 1,970 0.250 1,660 0.313 1,390 0.375 1,160 0.438 970 0.500 810 0.563 680 0.625 580 0.688 490 0.750 420 0.813 360 0.875 310 0.938 270 1.