Magnetic Flux Density Converter

Magnetic flux density — often called the B field — measures how concentrated a magnetic field is at a specific point in space: the amount of magnetic flux passing through a unit area perpendicular to the field direction. It's the quantity that determines how strongly a magnet attracts, how much torque a motor produces, and how detailed an MRI image can be.

Our Magnetic Flux Density converter supports the SI unit, tesla (T), along with weber/square meter (dimensionally identical to tesla) and weber/square centimeter and square inch for different area scales. Maxwell-based units — maxwell/square meter, centimeter, and inch — express the same quantity using the CGS unit of flux. Gauss (Gs, G), the CGS unit of flux density itself, remains extremely common in permanent magnet specifications and older physics references (1 tesla equals exactly 10,000 gauss). Line/square centimeter and line/square inch are older, largely synonymous terms for maxwell-based density, and gamma is a specialized small unit — exactly one nanotesla — used almost exclusively in geomagnetism to describe subtle variations in Earth's magnetic field.

To use the converter, select your starting and target units from the dropdown lists and enter a value — the result is calculated instantly to up to 12 significant digits. For example, converting a clinical MRI scanner's field strength of 1.5 T to gauss gives exactly 15,000 G, a conversion needed constantly when comparing modern SI-based equipment specifications to gauss-based historical or manufacturer literature.

Magnetic flux density values span an enormous range in practice: Earth's magnetic field at the surface is only about 25-65 microtesla, a small refrigerator magnet reaches roughly 5 millitesla, strong neodymium permanent magnets can exceed 1 tesla at their surface, and clinical MRI machines operate at 1.5 to 3 tesla (with research and industrial magnets going even higher). Flux density conversions matter in permanent magnet selection and motor design (torque and holding force scale with flux density), MRI and scientific instrumentation (field strength directly determines imaging resolution and signal quality), geomagnetism and paleomagnetism (measuring and interpreting Earth's magnetic field and its historical variations, often in gamma/nanotesla), and general electromagnetic engineering, where flux density values must be kept below a material's saturation point to avoid excessive core losses in transformers and inductors.

All conversion factors used in this tool are drawn from standard, internationally recognized unit definitions, so results are dependable for magnetics engineering, MRI and instrumentation specification, and physics research. The converter is free, requires no account, and works equally well on desktop and mobile devices.

Magnetic flux density multiplied by area gives total magnetic flux, and dividing flux density by a material's permeability gives the magnetic field strength required to produce it — so this converter is frequently used alongside the Magnetic Flux and Magnetic Field Strength converters elsewhere in this section when fully characterizing a magnetic circuit.