Magnetic Field Converter

Tesla, gauss, and magnetic field strength A/m (μ₀ relationship in vacuum).

The starting value is chosen rather than arbitrary: 0.00005 tesla is fifty microtesla, close to the strength of Earth's field at the surface, and it comes back as 0.5 gauss and 39.788736 amperes per metre. Tesla is the base and gauss is its CGS counterpart at a flat ten thousand to one, so those two columns are the same measurement in two traditions. The A/m column is not. Flux density B, measured in tesla, and field strength H, measured in amperes per metre, are distinct quantities linked by B = μ₀H, and the constant used here is exactly 4π × 10⁻⁷ — the value that was true by definition until the 2019 revision of the SI made the permeability of free space a measured quantity instead, differing in the tenth significant figure. That link holds only in vacuum or air. Introduce iron and the relationship becomes B = μ₀μrH with a relative permeability in the hundreds or thousands, so the amperes-per-metre figure this page reports for a field inside a core will be wrong by that entire factor. One behaviour sets this converter apart from its neighbours: it does not floor your entry at zero. A negative value passes straight through and every column changes sign with it, which is correct for a vector quantity where the sign records direction. Missing are the oersted, the CGS partner to gauss at 79.577 A/m each, and the weber and maxwell, which measure total flux rather than flux density. Tesla is rounded at twelve decimals, so anything below a picotesla flattens to zero.