I fly small a/c B738 in comparison to these guys. I did fly B767's -200 & -300, but the weight range was not too drastic. As suggested I have a 'feeling' for the correct figures. Reading this thread I now appreciate the spectrum of weights the A340 & B777 -ABC, -FGH, - XYZ can throw at you. Thus it is not quite so easy as I would have expected. Having a 'feeling' for the numbers might not be quite so instinctive as many of us might have thought. Still.......