Question: how many carbs and calories in a gin and diet tonic?
Answer: Each ounce of tonic water has about 2.5 grams of carbs. Gin has zero carbs. So, a regular Gin Tonic, with 3 ounces of tonic, is about 130 calories and 7.5 grams of carbs, all in the form of added sugar (as much carbs as half a slice of bread).