- Dog breeds
- Small breed
- Terrier group
- Origin: United States
The Rat Terrier is a lively, smooth-coated American farm terrier that comes in two size varieties. The AKC breed standard sets Miniatures at 10–13 in and Standards at over 13 up to 18 in, and Chewy lists adults at 10–25 lb. As a small breed on our scale, the Rat Terrier usually reaches adult weight at around 10–12 months, with Miniatures at the faster end. This page includes a Rat Terrier growth chart by age, a size calculator preset for the breed, and sourced guidance on lifespan, health, exercise and feeding.
How big do Rat Terriers get?
According to the AKC standard (height) and Chewy (weight), adult Rat Terriers weigh 10–25 lb (4.5–11.3 kg) and stand 10–18 in (25–46 cm) at the shoulder, with the same range for males and females. That makes the Rat Terrier a Small breed on our size scale.| Rat Terrier | Weight | Height |
|---|
The breed comes in two size varieties: Miniature, 10–13 in, and Standard, over 13 up to 18 in. The AKC standard sets no weight.
Many healthy pets fall outside the show standard, especially from working or pet lines. Use body condition, not the scale alone, to judge a healthy weight.
Rat Terrier growth chart: weight by age
| Age | Typical weight |
|---|---|
| 8 weeks | 4.7 lb2.1 kg |
| 3 months | 7.7 lb3.5 kg |
| 4 months | 9.9 lb4.5 kg |
| 6 months | 13 lb6 kg |
| 9 months | 16 lb7.3 kg |
| Adult (10–12 months) | 18 lb7.9 kg |
When is a Rat Terrier full grown?
Small breeds like the Rat Terrier reach their adult weight at about 10–12 months. Most of the growth happens early: by 6 months a typical Rat Terrier is around 13 lb, after which weight gain slows down as the dog fills out.How we calculate this: each figure is the midpoint of the breed’s adult weight range multiplied by the share of adult weight a small-size puppy typically reaches at that age (WALTHAM growth standards, Salt et al., 2017). It is the same model used by our Dog Size Calculator.
Rat Terrier puppy size calculator
Enter your puppy’s current age and weight to estimate how big your Rat Terrier will be as an adult. The calculator is preset for the breed.Dog Size Calculator
Predict how big your puppy will get — estimated adult weight from its current age and weight.
Best from ~8 weeks on; very young pups are less predictable.
Weigh on a flat scale, ideally before a meal.
Not sure? Use the size of the parents, or the larger parent for a mixed breed.
Males often finish a little heavier than females.
| Age milestone | Projected weight |
|---|
Dog breed weight chart (lb & kg) by size
| Size | Adult weight | Full-grown | Example breeds |
|---|---|---|---|
| Toy | 2–12 lb / 1–5.5 kg | ~8–10 mo | Chihuahua, Maltese, Toy Poodle, Pomeranian, Yorkie |
| Small | 12–25 lb / 5.5–11 kg | ~10–12 mo | Shih Tzu, French Bulldog, Mini Schnauzer, Mini Aussiedoodle |
| Medium | 25–50 lb / 11–23 kg | ~12–14 mo | Beagle, Border Collie, Cocker Spaniel, Std. Aussiedoodle* |
| Large | 50–100 lb / 23–45 kg | ~15–18 mo | Labrador, Golden Retriever, German Shepherd, Boxer |
| Giant | 100 lb+ / 45 kg+ | ~18–24 mo | Great Dane, Mastiff, St Bernard, Newfoundland |
*Standard Aussiedoodles span medium–large (≈40–70 lb / 18–32 kg); Mini Aussiedoodles are small (≈15–35 lb / 7–16 kg).
How it works: puppies of a given size reach a predictable share of their adult weight at each age. The tool divides your puppy's current weight by that share to estimate the adult figure, shown as a range.
Disclaimer: estimates for planning only — not veterinary advice. Growth varies with genetics, sex, nutrition and neuter status, especially for mixed and giant breeds. Keep records and consult your vet.
Sources: Salt et al., PLOS ONE 2017 (WALTHAM growth standards) · AKC — when puppies finish growing
Rat Terrier temperament and personality
Rat Terriers are bright, energetic and affectionate, and usually less scrappy than many other terriers. They are eager to please and quick to learn, which makes them good at agility and other dog sports. They are loving with family and often good with children, though they may be reserved with strangers. Their hunting instinct is strong, so small pets and loose rodents are at risk.-
Energy level4/5
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Trainability4/5
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Good with children4/5
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Shedding3/5
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Barking3/5
Ratings are BarnCalc’s own 1–5 scale, based on the breed standard and the sources cited below. Individual dogs vary.
History and origin
The Rat Terrier was developed on American farms in the late 1800s and early 1900s by crossing terriers such as the Fox Terrier and Manchester Terrier with breeds including the Whippet, Beagle and Italian Greyhound. Farmers valued these dogs for clearing barns of rats and hunting small game. Their numbers fell as farm poisons replaced ratting dogs, but enthusiasts kept the breed going. The AKC recognized the Rat Terrier in 2013.Rat Terrier lifespan and health
Most Rat Terriers live 12–18 years. Want to know how old that is in human terms? Try our dog years calculator, or estimate an individual dog’s outlook with the dog life expectancy calculator.Health conditions documented in the breed
- Patellar luxation
- Hip dysplasia
- Legg-Calvé-Perthes disease
- Heart disease such as mitral valve disease
- Primary lens luxation
- Allergies
Health tests to ask a breeder for
The breed’s parent club recommends these screenings for breeding dogs (ask to see the results for both parents):- Patella evaluation
- Hip evaluation
- Cardiac exam
- Primary lens luxation (PLL) DNA test
This is general information, not veterinary advice. Talk to your vet about your own dog.
Exercise and grooming
| Exercise | 45–60 minutes of walks and active play a day; secure fencing, as they dig and chase |
| Grooming | Brush weekly |
| Coat | Short, dense, smooth and glossy single coat |
| Low shedding | No – moderate shedder |
| Apartment living | Possible with daily exercise |
How much should a Rat Terrier eat?
A healthy, neutered adult Rat Terrier weighing 10–25 lb needs roughly 350–690 kcal a day. With a typical dry food of about 375 kcal per cup, that is about 0.9–1.8 cups a day, split into two meals. Active or intact dogs need more, while older or less active dogs need less. Always check the feeding guide on your food’s label.Breeding and pregnancy
Like all dogs, a pregnant Rat Terrier carries her puppies for about 63 days from ovulation. Most females come into heat about every 6 months.Is a Rat Terrier right for you?
A great fit for
Active families, people interested in dog sports, and owners with a securely fenced yard.Think twice if
Homes with pet rodents, owners who want a quiet, low-energy dog, or yards without secure fencing.Rat Terrier FAQ
When is a Rat Terrier full grown?
How big will my Rat Terrier puppy get?
How much should a 6-month-old Rat Terrier weigh?
How long do Rat Terriers live?
What is the difference between a Miniature and a Standard Rat Terrier?
Are Rat Terriers good apartment dogs?
More dog calculators
- Dog size calculatorHow big will my puppy get?
- Dog years calculatorDog age in human years
- Life expectancyLifespan by breed and size
- Gestation calculatorDue date and whelping window
- Heat cycle calculatorNext heat and fertile days
- Raw dog food calculatorDaily portions by weight
Sources
- AKC official breed standard
- Purina breed profile
- AKC: breed club recommended health tests
- Salt C. et al. (2017), growth standard charts for monitoring bodyweight in dogs of different sizes, PLOS ONE
Main photo: Jadenschaul, CC BY-SA 4.0, via Wikimedia Commons.
Reviewed by grupo barncalc.com on November 9, 2026. Estimates are for planning only and are not veterinary advice.