Which is larger: a rat or a guinea pig? - briefly
A guinea pig generally surpasses a typical rat in both length and mass; adults reach about 20–25 cm and 700–1200 g, whereas common rats average 15–20 cm and 300–500 g. Consequently, the guinea pig is the larger of the two.
Which is larger: a rat or a guinea pig? - in detail
The size comparison between the common brown rat (Rattus norvegicus) and the domestic guinea pig (Cavia porcellus) can be expressed through standard morphological metrics: body length, tail length, and adult weight.
Body length, measured from the tip of the nose to the base of the hindquarters, typically ranges from 20 cm to 25 cm in rats, while guinea pigs average 20 cm to 30 cm. The upper bound of the guinea pig’s length exceeds that of the rat, indicating a generally longer torso.
Tail length distinguishes the two species. Rats possess a tail proportionate to their body, measuring 15 cm to 20 cm, whereas guinea pigs lack a tail entirely. Consequently, overall linear dimension (including tail) remains greater for rats only when tail length is added, but the combined head‑body length still favors the guinea pig at its maximum size.
Adult weight provides a clear metric of overall bulk. Typical laboratory rats weigh 300 g to 500 g, with some large individuals reaching 600 g. Guinea pigs exhibit a broader weight range, from 700 g to 1 200 g for standard breeds, and up to 1 500 g for larger varieties. The minimum guinea‑pig weight already surpasses the average rat weight, confirming greater mass.
Summarized comparison:
- Body length: rat ≈ 20–25 cm; guinea pig ≈ 20–30 cm → guinea pig can be longer.
- Tail: rat ≈ 15–20 cm; guinea pig = 0 cm → rat has additional tail length.
- Weight: rat ≈ 300–600 g; guinea pig ≈ 700–1 500 g → guinea pig consistently heavier.
Overall, the guinea pig exhibits greater overall size in terms of body length and mass, while the rat’s tail adds to its total linear measurement. The predominant factor for size assessment is weight, where the guinea pig exceeds the rat by a substantial margin.