E. Coli. Size

E. Coli. can be modelled as a cylinder, with volume roughly $1 \mu m^3$.

However, note that cell volume can vary significantly under different growing conditions (although it is not clear yet why). Typically, cells that grow faster, end up larger.

Single-cell mass is hard to measure. To achieve femtogram ($10^{-15}g$) precision, scientists measure the oscillation frequency of liquid moving back and forth in a hollowed-out cantilever.

For an interesting visual comparing e. coli to a sample yeast cells, see Cell Sizes.