How many joules are in 1 kcal?

1 calorie is 4.1868 joules. This is referred to (or was when I was at school a long time ago) as the 'mechanical equivalent of heat' and is worth remembering, you can say 4.2 joules to a good approximation.

So 1 kcal = 4,186.8 joules or 4.1868 kjoules if you prefer