I see a lot of studies about the importance of fuelling whilst in heavy training.
I'm 6 foot, 61Kg and 18 years old. Mileage is 75 mpw.
On a workout day, which is typically:
Am: 3 mile warm up + 4/5 miles of intervals + 2 mile warm down
PM: 4 miles + Weights
How many calories should I be eating?
Easy days are normally 9-11 miles with one day off.
Eat lots of veggies, complex carbs, and lean meats and you shouldn't need to count calories. Just eat slow and eat till you feel full.
How many calories are in 22 medium-sized bananas? That's your answer.
I totally agree with John. Don't worry too much about calories. You should worry more about your lean protein, complex carbs, and your unsaturated fat intake.
There are all types of calculators on the internet to determine the right amount of macronutrients you need to maintain or even gain muscle, if that's what your going for.
But if you don't want to hear that, then here is a good article -
http://running.about.com/od/nutritionforrunners/f/How-Many-Daily-Calories-Do-I-Need.htm
-Erik
Get on the website "my fitness pal" and it will tell you what you need based on your age, weight and training stats. Works well.
Calorie counting isn't worht it because it's impossible to estimate calorie burning OR calorie consumption better than 10%. You're better off doing what others have said.