When ordering fries at McDonald’s, many customers automatically choose between small, medium, or large without thinking much about the difference. But an experiment by The Food Theorists compared serving sizes from several fast-food chains using digital scales, examining the amount of food customers received for the price. The results suggested that the large serving can offer particularly good value.

According to the comparison, the price difference between medium and large McDonald’s fries can be relatively small compared with the additional amount of fries. In other words, customers looking for the most food for their money may get more value by upgrading rather than purchasing multiple smaller portions. However, prices and serving sizes can vary by location.

Small fries do have one interesting advantage: they can fit efficiently into their packaging. Because the container is smaller, there may be less empty space between the fries. Still, when the focus is on overall quantity, the larger serving generally provides more food in a single order.

Freshness also makes a noticeable difference. McDonald’s fries are best enjoyed shortly after they are served, while their texture is still crisp on the outside and soft inside. Steam trapped inside the container can make them lose some of that crispness, so leaving the package slightly open can help. Some restaurants may also accommodate requests for extra-crispy fries, depending on location.

Ultimately, there is no single best size for everyone. If you simply want a smaller portion, small fries may be perfectly reasonable. But if your priority is getting more fries for a relatively modest additional cost, the large size may be the better choice. Next time you reach the counter, it might be worth comparing the prices before deciding whether to go small—or go big.