Rat Terrier Puppy Weight Calculator

Calculate the adult weight for your Rat Terrier. Just type your puppy’s current weight and age, and see how big your puppy gets.

The Rat Terrier breed profile

Breed Overview

The Rat Terrier is an energetic, intelligent, and versatile American breed originally developed for farm work, especially pest control. Their ancestry includes several terrier types along with Whippets and Beagles, giving them both agility and a keen sense of smell. Rat Terriers are affectionate, highly trainable, and thrive as active family companions.

Size Category: Small to medium.
Growth tracking is important for Rat Terriers because their build can vary depending on lineage—some are more compact “miniature” types, while others are taller “standard” sizes. Ensuring steady, healthy weight gain is key to avoiding joint strain or obesity, which can affect their agility and long-term health.

Rat Terrier Growth Chart & Weight Ranges

Age	Average Weight (lbs)	Average Weight (kg)
4 weeks	2 – 3 lbs	0.9 – 1.36 kg
8 weeks	4 – 6 lbs	1.8 – 2.72 kg
3 months	6 – 9 lbs	2.72 – 4.08 kg
4 months	8 – 12 lbs	3.63 – 5.44 kg
6 months	10 – 16 lbs	4.54 – 7.26 kg
9 months	12 – 18 lbs	5.44 – 8.16 kg
12 months	14 – 25 lbs	6.35 – 11.34 kg

Gender Differences:

• Males typically weigh 2–5 lbs more than females at maturity.
• Males may have a slightly more muscular build, while females tend to be finer-boned.

How Much Bigger Will My Rat Terrier Puppy Get?

Most Rat Terrier puppies reach 50% of their adult weight by 4 months.
Rule of thumb: Double their weight at 16 weeks for a good estimate of adult size.

While many reach their full height by 8–9 months, they often continue filling out in muscle and chest width until about 12–14 months. Miniature lines will mature sooner than standards.

For more breed details, see the American Kennel Club Rat Terrier profile or the Rat Terrier Club of America.

Rat Terrier Growth Tips

Nutrition

• Use a small-breed puppy food formulated for higher metabolism.
• Feed 3–4 small meals daily until 6 months, then transition to 2 meals.
• Monitor calorie intake closely, as this breed can gain weight quickly when overfed.

Exercise

• Provide daily walks, play sessions, and interactive games to channel their high energy.
• Avoid overly strenuous jumping or high-impact activities until growth plates close (around 12 months).
• Puzzle toys and training exercises help keep their sharp minds engaged.

Health Watch

• While generally healthy, watch for patellar luxation and hip dysplasia in some lines.
• Dental care is important—small breeds are prone to tartar buildup.
• Keep up with regular vet checks to ensure growth stays on track.