Ml is a measure of volume. Inches is a measure of linear distance. The relation between them depends on how much volume you have per unit distance, as in a pipe or straw or eye dropper, for example.

A cubic inch is 16.387064 ml, so

A cubic inch is 16.387064 ml, so

**4 ml**is 4/16.387064 in^3,**about 0.244 in^3**.