What is the formula for strength of magnetic field?

The strength of a magnetic field can be calculated using the following formula:

$$\begin{equation} B = \frac{\mu_0}{4\pi}\frac{2\mu_m}{r^3} \end{equation}$$

where:

• B is the strength of the magnetic field, measured in teslas (T)
• $\mu_0$ is the permeability of free space, equal to $4\pi \times 10^{-7} \text{ T} \cdot \text{m}/\text{A}$
• $\mu_m$ is the magnetic moment of the magnet, measured in joules per tesla (J/T)
• r is the distance from the magnet to the point where the magnetic field is being measured, measured in meters (m)

This formula relates the strength of a magnetic field to the magnetic moment of the magnet and the distance from the magnet