Quick Answer
Browse rat growth charts and weight ranges below. Use our breed-specific charts to track if your pet is on target.
⚖️
0.5-1.5 lbs
Weight range
📏
9-11 in
Body length
♂️
Males
Much larger than females
📅
6 mo
Full size reached
📏Growth & Size Facts
Sexual Dimorphism
Bucks (males) weigh 450-650g; does (females) 250-450g. Males also have a broader build.
Rapid Growth
Rats grow fastest in the first 3 months. By 6 months they are near full size.
Tumor Awareness
Sudden weight gain in older rats, especially females, may be a mammary tumor rather than fat.
Tail Length
The tail is nearly as long as the body. It helps with balance and temperature regulation.
Frequently Asked Questions
How big do pet rats get?
Body length of 9-11 inches plus a tail of 7-9 inches. Males weigh 450-650g; females 250-450g.
When do rats stop growing?
Rats reach near-adult size by 6 months. Males may continue filling out slightly until 8-10 months.
More Rat Resources
Track Your Pet's Growth
Create a free profile for your rat to log weight checks, set reminders, and see personalized growth charts.
Start Tracking FreeTrusted sources: AKC Breed Standards · AVMA Pet Care