Got a Real World Weapons or Armour Question? Mk XI

[Yora]

Shortsword up to 70cm of length

Longsword from around that 70 to 1m, sometimes a bit more

Bastard sword up to 120 cm

And Greatsword for all above that

Would probably be just fine for what D&D 3.5 was trying to get across.

Which actually matches quite well for what we would consider a generic short sword or greatsword.
The length of a Roman gladius was about 65 to 80cm, the 14th century longswords are about 120cm and up. The Roman spatha is given on Wikipedia as about 70 to 100cm.