I dont advise people count calories from melons as they are so light. Its a bit like counting calories from tomatoes etc. Nobody gets enough calories from eating a lot of melons, so just start counting when you start eating bananas/dates etc.
Also another factor is that most melons are not as sweet as they should be so they are even more calorie negative. Counting calories from melons is a great way to ensure we stay in a undercarbed state, which is great if we want to continue chronic fatigue etc.
According to caloriecount, 150kcal for small, 188kcal for medium and 277kcal for large. But this is very inaccurate (error roughly at least 20%), because as you can see there is a significant difference between these numbers and also the likelihood of any cantelope fitting any of the three numbers is zero.
There are plenty of days during cantaloupe season that I mono these melons. I use fitday @277kcal each for the large, but I don't worry about going over what I would normally eat in a day. When I mono them I usually eat 4 for breakfast, 4-5 for lunch and then maybe a couple as snacks before sitting down for a dinner of about three of them.
In all of fruitland this is my favorite food. Local and super ripe just off the vine is unbeatable. If you mono them you get a feel for what is satiating for you. When I get in at least 10-11 cantaloupe daily I am not undercarbed and therefore have no issues with cravings of hunger or desire cooked foods.