Presumably there is a caterer who will take care of logistics like stems, so not really at issue here.
175 people…any kids? Let’s say not. I’d assume somewhere around 25 - 30 won’t drink at all or will nurse a drink. On the other end of the spectrum, in my experience, except for wine geeks, the heavy drinkers are going to move to beer and liquor. Of the solid wine drinkers, very few would drink a whole bottle, and most wouldn’t drink a half. It’s probably fair to say you’ll have roughly 100 - 125 people consuming a moderate amount of wine. If all those people drank a half a bottle (which they won’t), you’d need about 60 bottles. That’s what I think is likely to consumed. But you need more than that because having too much is okay, running out is not.
To be safe, I’d err on the heavy side for champagne or sparkling, especially if there’s a toast. Something gets poured for everyone and a lot of people won’t even drink it, much less ask for more of it (most people still don’t think of champagne as what you drink with a meal, go figure). 3 cases of champagne.
With a warm afternoon and I assume and early-ish dinner, I’d go with 2-3 cases of white and 3-4 cases of red. You don’t need any sweet wine - it never gets consumed at large events, except by one person who drinks only that. Like Charlie, you’ll almost certainly have a bunch to bring home, but you’ll be safe.
So 8 - 10 cases depending on how safe you want to be. That’s my round about way of getting to exactly where Jonathan’s basic rule of thumb of 2.5 glasses per person would have gotten me with a lot less effort.
If you go the corkage route I suggest you ask your supplier if you can return unopened bottles for a refund. We’ve done this in the past for a couple of events and the wine shop was willing to take back reds (but not whites). If you can bear the hassle of holding onto and transporting the bottles, this allows you to order enough to be sure you won’t run out without wasting your hard earned cash.
People drink wine at weddings? My move is usually 2-4 whiskey drinks and then beer for the rest of the night so I can still stand!!
Assuming the bar is still open during dinner, just let people order their own drinks from the bar, and stop worrying about the small details. That’s for your SO to deal with lol
