Buying Alcohol

I am getting married in 2 weeks & would like to know how much alcohol to buy. We are planning on serving beer, wine, champagne, soda, water at the reception. There will be 45 people & 7 of those don't drink or are children. Also, when should I buy it - I'm planning on going to Costco for all or most of it.

Typically 60% of your guests will drink wine and the other 40% will drink beer. On average we estimate that guests will have 1 drink per hour each. Usually guests will have only 1-2 glasses of champagne for a toast (you can get approx 5 glasses per bottle) On average your guests will have 2-3 non alcohlic drinks each. If it's a hot day and you're outside make sure you have plenty of water available.
You can buy the beverages anytime you'd like, just make sure it's at least 1 day before your event so you can chill everything.