How long are squid arms?

That varies enormously depending on the squid.

Most squid are less than 60 cm long, with something between 1/3 and 2/3 of that being the body and the rest their tentacles. The arms are noticeably shorter - anywhere from 1/4 the length of the body to about equal in length to the body.

The giant squid can reach 13 m long - with about 2/3 of that being the tentacles. The arms are about half the length of the tentacles - about 4 m

The colossal squid may grow to 14 m - with about 1/2 of that being the tentacles. The arms are a bit shorter - around 5 m.