A bottle of wine = how many kilos of grapes?

In general, the containers answer this question by their ... capacity. It is no coincidence that wine bottles have 70 or 75 cl capacity. The real question lies rather in this mysterious difference of 5 cl.

Here is what I suppose: a kilo of chasselas (grapes with a relatively good yield of juice) gives approximately 78 cl of grape juice still containing solids which will be removed before fermentation, for a loss of volume of 4-5%. So it will be about 74-73% of the kilo of grapes that will become wine after fermentation. This, with the development of yeasts, generates a new loss of 1-2%. The various cellar operations (racking, pumping and filtration) until bottling generate some losses whose percentage varies by about 1% depending on the volumes treated.