Hello,
Well that depends on the track system: 027, Lionel Fastrack, Atlas..etc.  Most systems have 30 inch track sections(may be a bit more, but not too much) as the longest track.  Not sure about tubular track but I believe those are in the 35-40 inch range.  Either way it will require quite a few sections to go around your walls.    I have a Lionel Fastrack layout and 30 inches is the longest section.