A standard serving of wine is five ounces at 12% alcohol by volume.
This means you get Five glasses per 750ml/26oz bottle.
Follow three steps when estimating your needs:
100 "standard drinks" = approximately
Beer - 100 x 341ml / 12oz bottles
Wine - 20 x 750ml / 26oz bottles
Suppose you expect 200 people to be drinking at your event. The recommended number of drinks you need is 800 (4 x 200). Let's further suppose that you expect about half of the people to drink beer and the rest to be divided between spirits and wine. The 800 "standard drinks" required would be divided as follows:
400 bottles of beer (4 x 100)
40 bottles of wine (2 x 20)
12 bottles of spirits (2 x 6)
Remember to please drink responsibly and don't drink and drive.