thanks to all..so if i buy something and it has 180 calories per 100g ,all i do is weigh it till its 100g to get the 180 calories.
Yes, and if you only want 75g or 30g of something for example, take the figure given for 100g (in that case 180cals) and multiply it by 0.75 or 0.30 to get the amount you're going to be eating, it's quicker & easier than dividing the 100g sum by 100 to get the calories per 1gram, then multiplying it by 75 or 30 or whatever.
and also do i put the food on the scale or in a plate etc??
Depends on what works best, most scales have a way of setting weight on them (such as a plate) then resetting to zero so that only new stuff added on will count, sometimes that button or feature is called Tare (better explanation
here).
I prefer to use other containers, eg plates or tupperware boxes, on my scales so as to not mess up the jug provided or have to keep washing it - if you weigh raw meat, eggs or fish that's especially important.
(This might lean towards being a bit obsessive but I actually weighed ALL my plates, bowls and dishes + saucepans empty and dry, and then noted them in the back of my calorie count book, so if I need to weigh them with something in I know right away how much to subtract for the container... this may be abnormal, so just mentioning it!
)
i would love to eat potato wedges and measure them to get exact calories,..does the calories stay the same before oven cooked? thks
No, things like potato, bread and meat shrink when you cook them because they lose water, baked potato for example shrinks by as much as 30% in a standard fan oven, whereas grains and anything that's hard which you cook to soften it (beans, pasta etc) expand with the water, so it's best to weigh EVERYTHING raw (because you can't calculate the exact shrinkage/expansion) and double-check as well that you're going by calorie meaurements for raw quantities, eg a lot of pasta or rice packages will have a sum for 75g cooked which is VERY much less than 75g raw/uncooked rice.