Picture yourself hosting a cozy dinner with friends. The table is set, the food is ready, and you’ve just opened a bottle of red wine. You pick up the bottle, reach for the glasses—and suddenly wonder:

How much wine should you actually pour?

This simple question has sparked plenty of debate. If you look at four wine glasses filled to different levels, which one represents the proper pour?

At first, the answer may seem obvious. One glass contains barely a sip, another looks moderate, while another is filled almost to the rim. But the correct amount isn’t simply about how full the glass looks.

To understand the best pour, it helps to consider wine glass design, aroma, swirling, serving size, and wine etiquette.