Far from a bar magnet its field approaches that of a point dipole: B_axis = mu0 m / (2 pi r^3) and B_equator = mu0 m / (4 pi r^3), a ratio of 2. The check compares the two-pole model with those formulas at 5, 10 and 20 magnet lengths.

The magnet is modelled as two magnetic poles +-q a distance L = 6 cm apart (m = qL). Each pole gives a Coulomb-like field B = mu0 q / (4 pi r^2). Field lines leave the north pole and enter the south pole; a compass needle aligns with the total field, including the uniform Earth field. Where the magnet field cancels the Earth field there are neutral points.

On the axis B = mu0 m / (2 pi r^3) and on the equator B = mu0 m / (4 pi r^3) for r much greater than L; both decay as 1/r^3, much faster than a monopole 1/r^2. The finite-length correction is about (L/2r)^2.

Simplifications: real magnets have distributed magnetisation rather than point poles; hysteresis and shape effects are ignored.