Estimating a fitting vessel size for a reaction to be performed is a common lab task. Espresso ELN supports this by calculating the sum of the weights and volumes of all materials within a selection range. The resulting value is displayed at the bottom of the selection context menu, which appears after dragging the mouse over the desired area:

Although the result is displayed in volume units, this is an approximation of the actual total volume after mixing liquids and solids. This sum is only displayed if more than one material is selected.