How many calories should I be getting each day?

I'm a runner. XC and Track. As of today i had less than half of a meal replacement bar. But due to the fact its loaded with calories, i had about 80-90 from just that, even if it was less than half. And then for dinner i had a weight watchers pasta meal that had 320 calories in it. I just want to know...how much should i really be getting? I'm not going to get into my eating problems and all that, but i would just like to know.