How much does a single rat weigh? - briefly
A typical adult brown rat (Rattus norvegicus) weighs between 300 g and 500 g, with most individuals around 350 g. Smaller species, such as the roof rat, usually fall in the 150 g–250 g range.
How much does a single rat weigh? - in detail
The weight of an individual rat varies with species, age, sex, and health status. Laboratory strains such as the Sprague‑Dawley or Wistar typically reach a mature mass of 250–350 g (8.8–12.3 oz). Wild brown rats (Rattus norvegicus) commonly weigh between 200 and 300 g, with some large males exceeding 400 g (14 oz). Juvenile pups weigh only a few grams at birth (approximately 5–7 g) and double their mass each week during the first month.
Key factors influencing body mass include:
- Genetic line – selective breeding for size produces consistent weight ranges.
- Sex – males generally outweigh females by 10–20 %.
- Dietary regimen – high‑calorie feeds accelerate growth; restricted diets reduce adult weight.
- Environmental conditions – temperature and cage density affect metabolism and fat deposition.
- Health – disease or parasites can cause weight loss; obesity results from overfeeding.
Measurement practices recommend using a calibrated digital balance with a capacity of at least 1 kg and a readout precision of 0.01 g. Animals should be weighed at the same time of day, preferably after a brief fasting period, to minimize fluctuations caused by recent food intake. Recording weight weekly during growth phases provides accurate growth curves for research or breeding programs.
In summary, a typical adult rat weighs between 200 and 350 g, with variations dictated by genetic background, sex, nutrition, and environmental factors. Accurate assessment requires standardized weighing protocols to ensure reproducibility across studies.