To calculate how much liquid remains for a particular bottle, WISK uses a combination of a few factors:

- Product's
*full bottle weight*— weight of the bottle and its contents when it is full - Product's
*tare weight*— weight of the empty bottle excluding the liquid inside -
*Liquid's density*— necessary to convert weight into volume -
*Spout weight*— to account for the added weight of various spout types

Here is a simplified outline of the calculation process:

- Get the weight of the partially filled bottle from the Bluetooth scale and subtract any added weight from the spouts
- Check to see what the bottle's full weight is
- Check to see what the bottle's empty weight is — if we do not have the empty bottle weight, we can use the bottle's volume and the liquid's density to determine this
- Compare the full/empty bottle weights to the partial weight in (1) to determine the proportion of the bottle's contents that remain