When Do American Bullies Stop Growing — Full Size Timeline

Majestic Bully Puppies · American Bully Guide

When Do American Bullies Stop Growing — The Two-Phase Answer

When do american bullies stop growing is one of the most common questions new owners ask — and the answer is more complex than a single age. American Bullies go through two distinct growth phases: height growth driven by growth plate closure, and body mass development driven by muscle maturation. These two phases end at different times.

• Height growth ends at 12 to 16 months depending on class
• Body mass and muscle development continues until 18 to 30 months

An American Bully that looks lean or narrow at 12 months is completely normal — the bulk comes in the second phase. Never judge a Bully’s final size at one year old.

When Do American Bullies Stop Growing — By Class

Pocket American Bully

Pocket American Bullies are the fastest to mature. They reach full height between 10 and 12 months and full body mass between 14 and 18 months. By 18 months a Pocket Bully is essentially at its adult size.

Standard American Bully

Standard American Bullies reach full height around 12 months and continue filling out in body mass through 16 to 20 months. Most Standard Bullies are fully mature by 20 to 22 months.

XL American Bully

XL American Bullies reach full height at 12 to 14 months but do not reach full body mass until 18 to 24 months. It is entirely normal for an XL to look lean at 12 months — the characteristic wide chest and heavy muscle mass typically develops between 14 and 24 months.

XXL American Bully

XXL American Bullies are the slowest to fully mature of all classes. Full height is typically reached between 14 and 16 months with complete body mass and muscle development often not occurring until 24 to 30 months. Owners of XXL Bullies regularly report the dog continuing to visibly fill out and bulk up through age two and beyond.

Class	Full Height By	Full Body Mass By
Pocket	10–12 months	14–18 months
Standard	12 months	16–20 months
XL	12–14 months	18–24 months
XXL	14–16 months	24–30 months

Growth Plates — What They Are and Why They Matter

Growth plates are areas of soft cartilage near the ends of long bones where new bone tissue is produced during development. In American Bullies these plates typically close between 12 and 16 months depending on the dog’s size. Until growth plates close the bones are relatively soft and vulnerable to injury from high-impact activity.

This is why high-impact exercise — running on hard surfaces, jumping, rough play with larger dogs — should be limited until at least 14 months. Premature damage to growth plates can permanently affect bone structure and final adult conformation.

What Affects How Big Your American Bully Gets

Bloodlines

The bloodlines of the sire and dam are the single strongest predictor of final adult size. XL bloodlines from proven champion sires consistently produce larger puppies than Standard lines. At Majestic Bully Puppies every puppy carries Razor Edge and Gottiline champion bloodlines — genetics with a proven track record of producing the correct XL and XXL structure.

Nutrition During Growth Phase

Proper nutrition during the first 18 months is critical for reaching genetic potential. Underfeeding during the growth phase can permanently stunt development. Overfeeding causes rapid weight gain that stresses developing joints. See our complete American Bully Diet guide for feeding by age and class.

Neutering Age

Early neutering (before 12 months) can affect final size because sex hormones play a role in signaling growth plate closure. Dogs neutered early sometimes continue growing slightly longer and end up taller but with less muscular development. Discuss timing with your veterinarian.

Is My American Bully Done Growing

The simplest way to assess whether your Bully is done growing is to compare photos taken one month apart. If height and body mass appear consistent between photos and the dog is past 18 months for XL or 24 months for XXL — it is likely at or near its final size. Your veterinarian can also confirm growth plate closure via X-ray if you need certainty.

See our American Bully Growth Chart for expected weights by age and class, and browse our XL American Bully For Sale page for current availability.