On Thanksgiving, how much turkey is too much turkey and how much is too little? For those generous folks hosting a turkey day gathering, the decision about how big of a bird to cook can be difficult.

The key is first pinning down exactly how many guests are going to come for dinner. You don't want to plan on serving 10 people then four extras show up. Once the guest total is figured out, the best way to determine the size of your bird is through per-person math. 

Martha Stewart, the ever-trusted source for these types of decisions, recommends cooking about 1.5 pounds per person. That means if you have 10 guests coming to Thanksgiving dinner, your turkey should come in around 15 pounds. But, Stewart warns, smaller birds typically have less meat on their bones. If you're buying a bigger bird, say 15-20 pounds, 1.5 pounds is ideal. If you're buying a smaller bird, however, Stewart recommends 2 pounds per person.

Good Housekeeping takes a slightly different approach to its recommendations for turkey portioning. The magazine breaks the entire Thanksgiving meal down by servings in a handy chart, pegging a serving of turkey at 1 pound. But remember, Thanksgiving is a gluttonous holiday, so some people will eat more than one serving.

When many people think of Thanksgiving turkeys, they likely think of Butterball. The company posted a video about picking out a bird that recommends 1.5 pounds of meat per person, like Stewart.

The company also posted to its website a handy calculator that will take the guess work out of how many pounds of turkey you'll need. It takes into account the number of adults, the number of children and if your family is full of light or heavy eaters. You can find the calculator here

Remember it's always nice to have leftovers after Thanksgiving, so erring on the side of too much turkey is likely a smart move. Once your bird is picked out, check out how to brine it to make your Thanksgiving turkey even tastier.