  We introduce a systematic way to obtain expressions for computing the amount
of fundamental quantities such as helicity and angular momentum contained in
static matter, given its charge and magnetization densities. The method is
based on a scalar product that we put forward, which is invariant under the
ten-parameter conformal group in three-dimensional Euclidean space. Such group
is obtained as the static restriction (frequency $\omega=0$) of the symmetry
group of Maxwell equations: The fifteen-parameter conformal group in 3+1
Minkowski spacetime. In an exemplary application, we compute the helicity and
angular momentum squared stored in a magnetic Hopfion.
