How many ounces in a red wine glass?

How many ounces in a red wine glass? Red wine glasses have a decent range to them these days, going from a minimum of 8 ounces to a maximum of over 22 ounces. However, the standard red wine pour is 5 ounces, no matter what the glass size is. The rest of the head space in the glass is to maximize the air contact with the wine.