The calories in an orange and other related products are listed below. The edible part of an orange can be up to 85% water and therefore very low in calories. I have also listed out the calories in orange juices as well for reference. Though for more accuracy consult the nutrition label on the back of your orange juice carton. When it comes to juices, fresh juices are better than the carton variety. In addition, an Orange is an excellent source of vitamin C, an anti-oxidant which helps mop up free radicals in the blood. Free radicals have been shown to speed up the aging process.