Field-at-Distance Calculator

Field is computed from the exact on-axis analytical solution for a uniformly magnetized magnet. For a disc/cylinder (radius R, length L) at distance x from the face: B(x) = (Br/2)·[ (x+L)/√(R²+(x+L)²) − x/√(R²+x²) ]. Blocks use the arctangent solid-angle form.

Assumptions: field on the central axis only; axial (through-thickness) magnetization; a single magnet in free space with no ferrous parts, back-iron or bias magnet; and typical Br for the grade. Real sensor circuits with steel flux concentrators or a bias magnet will differ — use these numbers as the starting point and confirm with a bench measurement or FEA.

For a Hall IC, check the field at your maximum gap and worst-case hot temperature (Br falls ≈0.11%/°C) against the sensor's operate/release thresholds. Diametric (angle-sensing) magnetization is a different field pattern — ask us if that's your case. An axially-magnetized ring reverses its on-axis field over the bore near the face, so for ring sensor targets contact us for the specific geometry.