A lot of people ask me this question at tastings so here are some grapes stats:
It takes one cluster of grapes to make one glass of wine.
There are approximately 75 – 100 grapes to a cluster (depending on the grape type).
There are approximately four cluster to a 750ml bottle of wine.
One vine produces approximately 40 clusters.
One vine produces approximately 10 bottles of wine.
There are 5 glasses of wine per 750ml bottle.
There are 60 gallons to a barrel of wine.
One barrel yields 25 cases of 750ml bottles.
It takes 30 vines to make one barrel.
Most plantings have about 400 vines to an acre.
One ton yields between 500 – 600 bottles of wine.
One acre yields approximately 5 tons of grapes.
Dazzle and impress your friends. I bet they don’t know how many grapes there are in a glass of wine.
WiningWays 
You’ve got great insights about wine grapes, keep up the good work!
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Au contraire. What you might get from eating a 100 grapes everyday is… diabetes. Whole grapes contain far more sugar than wine by the glass. The resveratrol benefits you get from wine comes from the pips (seeds) and stems, not the fruit itself.