MagnetShop.com

This tool calculates flux density on the centerline of a disc magnet with a steel backplate, at a distance of X from the surface of the magnet.

(For your convenience, you can compare two magnets here.)

Scroll left and right
Inputs Magnet 1 Magnet 2  
Diameter Distance can be input in any units of measure as long as they are consistent to each other.
Thickness*
Distance X
Br (Gauss) Must be entered in gauss units.
Gauss at X

Results are in gauss.
     
*This is the orientation direction (the magnetic field flows through this direction)