What is the approximate diameter of most plant and animal cells?

The approximate diameter of a plant cell is between 10 and 100 micrometers. On average, animal cells are slightly smaller in diameter than plant cells, but still measure between 10 and 100 micrometers.

Because cells must constantly interact with their environment in order to enable the passage of nutrients and water through the cell membrane, they are limited in size by their surface-to-volume ratio. This ratio means that a cell can only grow so large before there isn't sufficient surface area on the cellular membrane to allow enough material to pass through to service the organelles and processes inside the cell.