not enough or too much?

libgrl

I have been running a lot (45 miles last week) along with biking and some strength training as I am training for a marathon in September. I keep track of my calories and try to stick to 1200 on days I don't exercise (which is almost never) and then days I do exercise I eat 1200 calories plus the calories I burned. I used an online calorie calculator for marathon training and it said I should be eating between 2200 and 3000 calories for the amount I run, which seems way too much.

http://www.marathon.ipcor.com/marathon-nutrition-calculator.htm

I am maintaining the same weight, which is fine for now, but I am always really hungry lately.
I am 5 foot 4 inches tall and weigh around 128 to 130 lbs.

Any advice?