𝗟𝗲𝘁'𝘀 𝗧𝗮𝗹𝗸 𝗔𝗯𝗼𝘂𝘁 𝗕𝗼𝗼𝘇𝗲! 𝘋𝘐𝘠 𝘉𝘢𝘳 - 𝘏𝘰𝘸 𝘮𝘶𝘤𝘩 𝘢𝘭𝘤𝘰𝘩𝘰𝘭 𝘥𝘰 𝘺𝘰𝘶 𝘯𝘦𝘦𝘥? Always start with an online calculator, these are pretty good at giving you a starting point - but do not blindly follow them. They are general for a reason. Your guests and your wedding are unique.
A good rule of thumb is to assume that each guest will consume 1 drink per hour. So for a 2-hour cocktail hour and a 4-hour dance, for 100 guests, you'll want 600 'drinks'.