From high school physics 1 calorie will heat 1ml of water 1 degree Fahrenheit (I think)
One Kilo calorie often written Calorie (with a capital C) will heat 1000 ml of water 1 degree Fahrenheit .
They are measuring the same thing and as ray said that for nutritional purposes it would be uncommon for the small calorie to be used.
Calories are a way of measuring energy the same as joules just the size of the unit is different.
An example is in distance is distance can be measured in miles or kilometres.
Both measure distance but the size of the unit is different.
A kilometre contains 1000 metres. But many people would think it inappropriate to measure the distance between towns in metres but is could be done.
Equally
A Calorie (Capital C) contains 1000 calories (small c). But many people would think it inappropriate to measure the energy in food in calories (small c) but is could be done.
I would think that 99.9% of the population find this confusing.
Perhaps we should be asking when we have been metric in this country for a long time why do we still use Calories rather than Kj.
