What length can a rat be? - briefly
Rats typically measure 15–23 cm (6–9 in) in body length, with tails of comparable size, giving a total length of roughly 30–38 cm (12–15 in).
What length can a rat be? - in detail
Rats exhibit considerable variation in size, primarily between the two most common species. The brown rat (Rattus norvegicus) typically displays a head‑body length of 20–25 cm, with a tail roughly equal to or slightly shorter than the body. Total length therefore ranges from 30 to 45 cm. The black rat (Rattus rattus) is generally smaller, with head‑body measurements of 15–20 cm and a tail that often exceeds the body length, producing a total length of 25–35 cm.
Extreme measurements have been recorded in laboratory and wild populations. The largest brown rat documented reached a head‑body length of 30 cm and a tail of 28 cm, giving a total length of 58 cm. Conversely, juvenile specimens may measure as little as 5 cm in head‑body length, with proportionally short tails.
Factors influencing individual dimensions include:
- Genetic lineage: distinct subspecies display consistent size differences.
- Sex: males generally exceed females by 10–20 % in body length.
- Nutrition: abundant, high‑quality food sources promote greater growth.
- Habitat: urban environments often support larger individuals due to reduced predation and plentiful waste.
Standard measurement protocol separates head‑body length from tail length. Researchers place the animal on a flat surface, align the snout with a ruler, and record the distance to the base of the tail; the tail is then measured separately from its base to the tip. Total length is the sum of these two values.
When compared with other rodents, rats occupy a mid‑range size. House mice (Mus musculus) average 8–10 cm total length, while hamsters (Cricetinae) range from 12 to 20 cm. Larger rodents, such as the capybara (Hydrochoerus hydrochaeris), exceed 130 cm in total length. This context underscores that rat dimensions are substantial among small mammals but remain far below the size of the largest rodent species.