In Piecemeal, using the Unit Conversion Tool will allow you to use multiple different types of unit of measurement for one single inventory item.
Canned tomatoes can be bought as 6 cans of 2.84L, but what happens when I want to use 10 KG of canned tomatoes in a recipe.
Here is where the Conversion Tool comes in handy. By simply entering two comparable conversion value, you will be able to use volume AND mass as units of measurement.
How to set conversion values
In the inventory item's file, scroll to the bottom, all the way to Unit Conversions. There you will find the three main types of unit of measurement : Weight, Volume, Units
Enter the amount to convert (usually the "Each package contains" value)
Enter the amount equal to the amount previously entered
NOTE: You need at least 2 values to compare. You can compare a maximum of 3 different types of unit of measurement