Allow calculations in quantity and serving size

[davidhealey]

I think it would be cool if you could do simple maths in these fields and have the other fields update accordingly.

For example if an item is a 200g serving and you want to know what half of it would be you could just enter into the box 200/2 or 200*0.5. Obviously with 200 it's not difficult to work out in your head but if it was a more obscure value like 372.5g it would be very helpful.