How Many Grapes Does It Take to Make a Bottle of Wine

Last night, on the way home from working in our vineyard, my husband and I discussed how many grapes it would take to make a bottle of wine. At the moment, this is entirely theoretical because although we have a vineyard, we only have 500 survivors from our devastating winter of 2013, but it is still a good mental exercise. I cited Lucie Morton, who wrote the book Winegrowing in Eastern America which included this illustration:

When we discuss this question, my husband always refers to the linear feet of fruiting wire rather than the grapevine as the unit of measure. It would really be nice to know how many cases each row of vines can produce so today, I sat down to do some calculations.
If we take into account, my husband's insistence that the calculation must be based on the linear feet of fruiting wire, the following assumptions will be made: On average, there is a shoot every 4 inches or a fist's width apart and on average, each shoot produces 2 clusters of grapes. So, for our 760 linear feet, we will have approximately 2280 shoots or 4560 clusters of grapes.¹ I also assumed that each cluster of grapes was approximately 0.2 pounds based on information I found at the Cornell University website.² So, the calculation based on the linear feet of fruiting wire gives us this:

In back calculating, the above assumption gives us 3.75 tons per acre, which is about where we want to be when we are in production.

References:
1. Ben Beale, Grape Canopy Management, University of Maryland Extension.
2. Estimating and Adjusting Crop Weight in Finger Lakes Vineyards.
3. Mark Chien, Need Quality? Try Canopy and Fruit Zone Management Vermont and New Hampshire, Penn State Cooperative Extension.