Some weights:
Arming swords seldom weighed more than around 2-2.5lbs.
Longswords typically ranged between 2.5-3.5lbs.
Even the big Zweihanders of the late Medieval/early Renaissance period would seldom weigh more than about 6lbs. Swords heavier than that were the exception, and usually big ceremonial ones or wall hangers never intended to be actually used in combat.
There really was no such thing as light or heavy sword. They were ALL as lightweight as they could be made because they HAD to be in order to be able to actually use them them effectively. Even the broader, heavier-looking blades were lightened through the use of fullers or blade profile.
What you DID have was differences in the distribution of that weight.
Using the Oakshott classification for an example, a Type XVIIIb sword has much different handling characteristics than a Type XIIa, even though both were longswords. The former has a much more slender blade with an awl-shaped point, and was quite balanced between the cut and the thrust. By contrast the XIIa was broader with a less acute taper, making it much more focused on cutting. Yet both swords would weigh in along the same range (2.5-3.5lbs).
Type XIIa:
Type XVIIIb
This isnāt a matter of being poorly balanced, either, just that the two swords were made for different purposes; the highly-versatile Type XVIIIb rose in popularity during the early 15th century as plate armor became more widespread, because its slender blade was better-suited for piercing gaps in armor than the broader Type XIIa.
