How much does a male rat weigh? - briefly
Adult male laboratory rats typically weigh 300–500 g, with most common strains averaging about 350 g. Wild counterparts are lighter, generally ranging from 200 to 300 g.
How much does a male rat weigh? - in detail
Adult male rats typically weigh between 250 g and 500 g, depending on strain, age, and husbandry conditions. The lower end of the range represents young adults or smaller strains, while the upper end corresponds to mature individuals of larger breeds.
Weight is influenced by several variables:
- Genetic background – Sprague‑Dawley and Wistar rats commonly reach 300–350 g; Long‑Evans males often exceed 350 g; larger outbred stocks may approach 500 g.
- Age – Rats attain most of their adult mass by 10–12 weeks; weight stabilizes thereafter, with slight increases up to 24 weeks.
- Nutrition – Caloric density and protein content of the diet can shift body mass by 10–20 % within a cohort.
- Housing – Group housing may reduce individual weight relative to isolated animals due to competition for food.
Standard practice for obtaining accurate measurements involves using a calibrated analytical balance with a precision of at least 0.01 g. Animals should be weighed after a brief acclimation period, preferably in the early light phase to minimize metabolic fluctuations.
Understanding the typical mass of a male rodent is essential for dosing calculations, cage space allocation, and interpreting physiological data. Researchers should record strain‑specific baseline weights and monitor changes throughout experimental protocols to ensure reproducibility and animal welfare.