If you decide to guess at how much meat you'll need to feed guests for a meal, chances are one of two things will end up happening: either you'll end up short, leaving your guests unsatisfied and hungry or you'll wind up with a ton of leftovers. While the latter may not always be a bad thing, if you're on a budget or looking for extra food for the week; however if you want to purchase just the right amount to do so successfully, you must figure out how much meat to buy per person.
Plan the entire menu for your event before trying to calculate the amount of meat you will need. This way, if there are changes or decisions to be made about the menu, you won't have already purchased too large or small amount of meat. Making a detailed menu will help you minimize last-minute changes and give you a better idea of how much meat you will need.
Use your menu to help you assess how big of a portion the meat will provide for the meal. For example, if you are serving a main course of meat that also includes pasta and a baked potato, or as an appetizer, you will not need as much meat as if you were to serve steak with only a small side of vegetables.
If the meat will be an appetizer, multiply the number of guests you wish to serve by 0.2. Multiply the number of guests by 0.5-0.33 if the meat will be a part of the main course but will also include other filling components. If you are going to mix the meat into another dish, such as a curry or chili, multiply the number of guests by 0.25- 0.33. If you intend to serve the meat as the center of the meal with few -- if any -- accompaniments, multiply the number of guests you wish to serve by 0.75. The resulting numbers in these calculations will provide you with the number of pounds of meat you should purchase to feed your guests.