[sjtrny]

The hard part about this problem is getting the scale and thus volume of the objects right. How big is that bowl holding your cereal?

[millstone]

And is that Coke or Diet Coke?

[vidarh]

And have you "hidden" a dash of syrup or 100g of nuts under the milk.

But it'd be useful for rough estimates for things like restaurant meals, with the aid of a menu.

[rtpg]

panorama-like shot + obligatory 'token' in the shot should solve that, right?

[waps]

Do the same as humans do : it's 25cl ... point. You won't be far off the mark.

[vidarh]

You probably will be far off the mark. I realized once I started tracking my food seriously that 1) those glasses I have that I though were substantially bigger than those other glasses? They held the exact same amount; 2) the amount of calories I consume could easily vary by 30% or more depending on how full I'd fill my various glasses, plates or food containers.

[waps]

I don't think getting a 30% margin of error would be all that disastrous. How big is the error margin on people measuring ?

[ehsanu1]

A 30% margin of error would seem to make calorie counting practically useless.

[waps]

I seriously doubt anyone doing calorie tracking without scales achieves less than a 30% error rate.