  Electron-positron pair creation in supercritical electric fields limits the
net charge of any static, spherical object, such as superheavy nuclei,
strangelets, and Q-balls, or compact stars like neutron stars, quark stars, and
black holes. For radii between $4\times10^2$ fm and $10^4$ fm the upper bound
on the net charge is given by the universal relation $Z=0.71R_{fm}$, and for
larger radii (measured in fm or km) $Z = 7 \times 10^{-5} R_{fm}^2 = 7 \times
10^{31} R_{km}^2$. For objects with nuclear density the relation corresponds to
$Z \approx 0.7 A^{1/3}$ ($10^{8} < A < 10^{12}$) and $Z \approx 7\times10^{-5}
A^{2/3}$ ($A > 10^{12}$), where $A$ is the baryon number. For some systems this
universal upper bound improves existing charge limits in the literature.
