$\mathrm{Formula} \mathrm{for} \mathrm{calculating} \mathrm{the} \mathrm{mass} \mathrm{of} \mathrm{the} \mathrm{electron} \left({\mathrm{m}}_{\mathrm{e}}\right) \mathrm{i}s$

$\text{ Formula for calculating mass of electron }\left({\mathrm{m}}_{\mathrm{e}}\right)\text{ is }{\mathrm{m}}_{\mathrm{e}}=\frac{\mathrm{e}}{\left(\mathrm{e}/{\mathrm{m}}_{\mathrm{e}}\right)}.$

$\text{ where, }{\mathrm{m}}_{\mathrm{e}}=\text{ mass of electron in }\mathrm{kg}$

$\mathrm{e}=\text{ magnitude of the charge on the electron in coulomb (C) }$

Since, electrons are negatively charged, the charge on electron is -e.