In the sense of keeping things simple, the amount of calories in red wine is dependent on a couple of factors. First and foremost is the size of the glass relative to the pour. In other words, the amount of wine you pour into the wine glass. I tend to be a little heavy handed, and am always amazed when I order wine out how small a serving of wine is. Somehow I feel cheated.
A bottle of wine is supposed to have approximately 4-5 servings. However, because of my heavy handedness I rarely get 4 servings and have never reached 5 servings from a bottle of wine. I have a pour it like you mean it attitude.
So just how much is 3.5 fluid ounces of red wine?
To give you an idea of how much 3.5 fl oz or 1/3 of a cup is appropriately 7 tablespoons.
A typical restaurant pour of red wine is about 5 ounces, so in general, if you figure about 25 calories per ounce of red wine the calories in a glass of red wine is about 125 calories.
With all things, moderation is the key; whether you are watching carbs or counting calories in red wine. My idea of a serving of red wine may be vastly different than someone else and is most certainly different than the restaurant industry's.
Life is simply too short to worry about how many calories your consuming in a single serving of wine. The most important aspect to remember is that if you are too consumed with counting calories just how much are you going to enjoy that glass of wine.
Worry less, drink more wine!