Scale/Gauge Comparison

[MountainMan]

The prototype of both cars is 40' long.
therefor is the N scale standard gauge 40' box car 40' / 160 long = 0.25'
and the HON3 scale 40' boxcar is 40' / 87 long = 0.46'

ps. The gauge (standard vs. narrow) is not of relevance for this calculation. It's the scale that counts.

That doesn't make any sense, since the standard N gauge boxcar is considerable larger than it's comparable NN3 counterpart. Narrow gauge is always smaller than standard gauge rolling stock, as any old photo of the two will easily show.