This calculator will calculate for you how many calories you use up in a run. Perhaps surprisingly, it only depends on the distance ran, and your weight.

Distance:	kilometresmiles
Weight:	kilograms pounds stone
Calories:

This calculator should be used as an estimate. The exact number of calories expended does depend on pace, age, sex, and base metabolical rate. It is however a good starting point, and will give you an indication of the requirements of your diet.