Use a measuring cup and scale to determine the correct size. Fill the measuring cup with the desired amount and note how many ml you need. See the steps below for visual examples.
 

Step 1

Place an empty measuring jug on a scale.
 

Step 2

Fill the measuring cup with the total weight of the product you want to pack.
 

Step 3

Read how many ml are in the measuring cup. Now you know what size you need!