How large do domestic rats grow? - briefly
Pet rats normally reach a body length of 20–25 cm (8–10 in) with a tail of similar size and weigh 300–500 g, though exceptionally large individuals can exceed 600 g. Size varies with strain, diet and genetics, but most mature adults fall within these dimensions.
How large do domestic rats grow? - in detail
Domestic rats typically reach a body length of 7 – 10 inches (18 – 25 cm), not counting the tail, which adds another 6 – 9 inches (15 – 23 cm). Adult weight varies with strain and sex:
- Standard laboratory or pet strain: 300 – 500 g (10 – 18 oz).
- “Fancy” varieties selected for coat or color: up to 600 g (21 oz).
- Dwarf or “miniature” lines: 150 – 250 g (5 – 9 oz).
Growth follows a predictable pattern. Pups are born hairless and blind, weighing about 5 g. By three weeks they are weaned and begin solid food, entering a rapid growth phase that lasts until roughly eight weeks of age. Most individuals achieve near‑adult size by five to six months; thereafter weight stabilizes unless diet or health conditions change.
Factors influencing final size include genetics (strain selection), nutrition (high‑protein diets promote lean mass), and housing conditions (stress can suppress growth). Males generally exceed females by 10 %–20 % in both length and mass. Seasonal breeding cycles do not affect size, as domestic rats reproduce year‑round under controlled environments.
In summary, a fully grown pet rat measures about 13 – 19 inches total length and weighs between 150 g and 600 g, with the exact figures determined by breed, sex, and husbandry practices.