Formula Circular Motion in the Magnetic Field Period Magnetic field Electric charge Mass
$$T ~=~ 2 \, \pi \frac{ \class{brown}{m} }{ |q| \, \class{violet}{B} }$$ $$T ~=~ 2 \, \pi \frac{ \class{brown}{m} }{ |q| \, \class{violet}{B} }$$ $$\class{violet}{B} ~=~ 2 \, \pi \frac{ \class{brown}{m} }{ |q| \, T }$$ $$|q| ~=~ 2 \, \pi \frac{ \class{brown}{m} }{ \class{violet}{B} \, T }$$ $$\class{brown}{m} ~=~ \frac{ |q| \, \class{violet}{B} \, T}{ 2 \, \pi }$$
Period
$$ T $$ Unit $$ \mathrm{s} $$ Time needed for the charge in the magnetic field to make exactly one revolution.
Magnetic field
$$ \class{violet}{B} $$ Unit $$ \mathrm{T} = \frac{\mathrm{kg}}{\mathrm{A} \, \mathrm{s}^2} $$ Magnetic flux density, which indicates how strong the external magnetic field is in which the charge is orbiting.
Electric charge
$$ |q| $$ Unit $$ \mathrm{C} $$ Magnitude of a positive or negative, circling charge. Sign of the charge makes no sense here, because otherwise the time would be negative.
Mass
$$ \class{brown}{m} $$ Unit $$ \mathrm{kg} $$ Mass of the charged particle.