Quite simply, it’s 750ml. Or about 25 ounces. (Ok, so it’s technically 25.36, but 25 should be close enough right? When’s the last time you didn’t spill anything?)
A more interesting question, how many ounces are there in a glass of wine? It’s less than you think, which also means that there are more glasses of wine in a bottle than you probably think.
In any case, there’s about 25 ounces in a 750ml wine bottle.
Also, if you’re wondering why a wine bottle is that size today. Think back to ancient times, glass wasn’t made in factories, but instead by people. 750ml is about the amount of air held in the average humans lungs. (here’s my write up on that one).