If you're asking yourself this question, you're ahead of the game. Buying too much cheese could lead to food waste, buying too little can be not great either. There is a common rule of 1 to 1.5 ounces (30-45g) of cheese per cheese per person. Whether or not you round up or round down depends on the answers to the following questions:

Will everyone be eating cheese? (some people might not).

Not just vegans don't eat cheese anymore, many people also have lactose allergies or sensitivity which makes it hard for them to digest dairy products. According to one report, the lactose-free dairy market is in a huge period of growth. Looking at the data, almost 90% of adults in East Asia suffer from lactose intolerance. Globally, 65% of the human population has a reduced ability to digest lactose after infancy. If you have a pretty good idea of who eats cheese in your friend/family group then you are better armed to determine how much cheese to buy, but, if you are unsure, you may want to plan for more lactose-free options, like vegetable sticks and hummus.

What other food will be served?

If you're planning on a large spread of food, you might want to adjust how much cheese you buy. For example, if you're planning on serving cheese as an hor d'oeuvres you want to make sure that whatever the full spread looks like at the end of the day is a reasonable amount of food to prevent waste.

How adventurous (read smelly) of cheeses are you looking for?

If you're all in on epoisses, you might be the only one at your gathering. The smellier or moldier the cheese, the less people, in general, would be into eating it. If you live in a country where all the different kinds of cheese are celebrated then you might get away with some more exotic cheeses, but other places, not so much. Depending on the crowd, you may want to limit the variety of your spread to some crowd favorites (e.g. brie, gouda) and buy smaller amounts of more adventurous cheeses.

Are you going for a variety of cheeses, or are you doing a single cheese? (e.g. a baked brie)

This is probably more straightforward than the others, but if you're planning on having several varieties of cheese on your cheese board, you should expect that your guests will eat relatively less of each individual cheese. Consider that you might want to forego the refrigerator aisle and ask your cheesemonger to cut the sizes you need. Prepackaged cheese are cut into standard sizes, but a cheesemonger can cut you smaller sizes, which will help you save money and potential waste.

Get a second opinion: ask your cheesemonger

If you're able, and have access to a cheesemonger in your area you can always ask them all of your questions. They can show you how much a certain weight of cheese looks like, or might be able to tell you more precisely how much of a specific cheese is enough for the number of guests, and which cheeses might not be as popular at your party.