The SI unit for flux density, or induction, is the tesla (T). This property is also referred to as the B field. In the equations from our Surface Fields article, we use a "B" to denote this term.
Unlike Magnetic Flux above, the Flux Density defines some size for the loop of wire in that example. Flux Density is a measure how many webers are squeezed into some area. In fact, webers per square meter is the unit for flux density. By definition, 1 weber per square meter (Wb/m2) = 1 tesla (T).
The conversion between gauss and tesla is an easy one: 1 tesla = 10,000 gauss.
Here's a confusing part: Many people call this, "field strength." We often refer to field strength in gauss. Technically, we should probably use the term, "magnetic flux density," though it's much more commonly called, "field strength."
We use flux density to express Surface Field.
We use flux density to describe the "field strength" at some distance from a magnet, used in our Pull Force Calculator and in the formulas given in our Surface Fields article.
We measure field strength with a magnetometer, expressed in gauss.
The average flux density here on the surface of the earth is about 0.5 gauss, though it varies from 0.22 to 0.6 gauss.
