Skip to content
How Big Will My Dog Get

How Big Will My Dog Get

Most breeders and veterinarians recommend adopting puppies at 8 to 10 weeks old. While the puppies might all seem like adorable little bundles of fur at that stage, there is a size difference depending on the breed and lifestyle conditions.

That brings all the curiosity about predicting adult size. It's like wanting to peek into the future and see your playful pup all grown up. That way, you'll prepare to tackle the dog's needs as it grows from a tiny ball of fluff into a majestic grown-up giant. For instance, you'll know the collar, harness, and crate sizes you'll need.

The good news is that there is a back-of-the-napkin math trick that veterinarians use to predict a puppy's adult size. It's not perfect, but it can give a general idea of how big your furry friend might become. Here is all about predicting your puppy's adult size, from factors affecting the size to the size calculator.

Predicting Your Puppy's Adult Size

Before adopting a furry roommate, you want to make sure you have the space and lifestyle to accommodate him comfortably throughout their life. For example, living with a Great Dane puppy in an apartment looks adorable but challenging when he is fully grown.

He might have accidents such as knocking over lamps when trying to navigate your furniture. No one wants a giant dog feeling cramped or a tiny dog feeling overwhelmed in a huge house. Or you wanted a working dog like the German Shepherd but ended with a lap dog like the Chihuahua.

Puppy weight calculators are like little weight prediction machines, taking into account factors like breed, current weight, and sex to give you a glimpse into your furry friend's future size. But before we get into using the calculator, let's see how these factors affect the puppy's adult size.


Every dog inherits a specific set of instructions from its parents. These instructions are like a complex recipe coded within their DNA, dictating everything from their physical characteristics like fur color and eye shape to more internal traits like disease resistance and blood type.

The DNA code isn't always exactly the same between parents and offspring. These mutations are like little typos in the recipe. The variations lead to new and interesting physical characteristics, like a slightly different fur pattern or a unique eye color.

Unlike traits controlled by a single gene, like eye color, size is controlled by multiple genes, each with a small effect. The effects of these genes are additive. So, if a puppy inherits genes from both parents that code for slightly larger size, they'll likely end up bigger than a puppy who inherits genes for a smaller size.

By selectively breeding dogs that fall within a desired size range, breeders slowly, over generations, influence the size profile of a breed. For example, Great Danes possess alleles promoting growth hormone production and extended growth plate closure. This allows for extended bone development, resulting in a massive frame.

Chihuahuas, conversely, have genes that limit growth factor production and promote earlier growth plate closure. This halts bone growth at a smaller size. As a result, the primary determinant of your puppy's adult size is the breed and genetics.

If it's a Great Dane puppy, expect the adult dog to weigh 100 to 120 pounds, with a standing height of 30 to 32 inches. If it's a Chihuahua, expect the adult dog to weigh 2 to 6 pounds, with a standing height of 6 to 9 inches. That's how serious selective breeding determines the dog's size.


A puppy's diet is like a magic potion for growth, but it's more than just about fueling them up with calories. Just like how you need the right materials and construction techniques to build a house, the puppy's diet requires the right nutrient composition for proper growth. Here are the things to consider.


Protein is the building block of muscles, bones, and tissues. Growing pups need more protein than adults, typically around 22.5% of their diet on a dry matter basis.  Without enough protein, puppies won't have the necessary materials to build strong, well-developed muscles.

Remember, dogs like the American Bullies are known for their stocky and muscular bodies. They look like walking tanks that can pull a small car. These dogs need the right amount of protein to bulk up and achieve that champion physique.

Otherwise, that broad chest and those powerful legs he's supposed to have won't get as sculpted as they could be. He might end up lighter and looking a little leaner, like a long-distance runner, than a weightlifting champ.


Puppies go through growth spurts, during which they seem to get bigger overnight. Fat is the source of energy. It helps provide the extra energy they need to support the rapid development of bones, muscles, and organs.

One gram of fat gives you nine calories, while carbohydrates and protein only offer four calories each. That's more than double the bang for your buck. Without enough fat, the body starts breaking down stored glycogen in the liver and muscles. The result is an underweight dog.  

Fat also helps with the absorption of fat-soluble vitamins such as vitamin A. That means the lack of fat content in a puppy's food reduces the absorption of vitamins. The result is a malnourished dog with stunted growth.  


Testosterone is the dominant sex hormone in males produced in the Leydig cells within the testicles. Females primarily produce estrogen in the ovaries. However, they also produce a small amount of testosterone in the ovaries and adrenal glands.

Testosterone increases the rate of protein synthesis in muscle cells. This means the dog's body uses protein more efficiently to build and repair muscle tissue. Think of it like a construction crew working faster with the right tools!

Also, testosterone helps activate satellite cells, which are like muscle stem cells. These cells have the potential to fuse with existing muscle fibers, making them thicker and stronger. It's like building an extension onto your existing muscle house.

Another thing is that testosterone directly stimulates the production of osteoblasts, which are the cells responsible for building new bone tissue. The result is dense and stronger bones. Testosterone levels range between 2 and 4 ng/ml in male dogs, and can fall below 1 ng/ml in female dogs.

Due to the higher testosterone levels in males compared to females, male dogs are usually heavier and larger. In any breed, expect males to be on the higher side of the size spectrum and females on the lower side. 


Just like in humans, health issues can make puppies not grow to their ideal adult sizes. Here are the common health issues that affect a puppy's growth and development.

Chronic Liver and Kidney Problems

The liver processes nutrients from food, breaks them down into usable components, and distributes them throughout the body for growth and repair. The kidney filters out toxins and waste products from the blood.

When there are issues with these two, the dog won't process and benefit from some of the nutrients in the food, resulting in stunted growth. Also, the buildup of toxins in the bloodstream makes it difficult for the body to absorb and utilize nutrients, affecting growth.

Hormonal Imbalance

The growth plates at the ends of long bones are made of cartilage. Hormones like thyroid hormone act as the architects, sending signals to tell the cartilage when to grow and eventually harden into solid bone.

If the thyroid gland isn't producing enough thyroid hormone, there are no proper hormonal signals to the growth plates. As a result, the plates might stay soft and cartilaginous for too long, hindering bone growth.

The good news is that thyroid hormone replacement therapy is available. This medication helps regulate hormone levels and allows the growth plates to function properly. 

Congenital Conditions

Hereditary genetic conditions can affect bone development and limit a puppy's growth. These conditions usually vary widely across dog breeds. That's why it's advisable to take your pup for regular checkups and discuss any concerns with your vet.

Puppy Weight Calculator

In most cases, the calculator uses the formula of Adult weight = (weight of the puppy/age of the puppy in weeks) * the number of weeks per year, which is 52. Considering that most pups are full-grown by around one year, the estimate is not far from the truth.

However, giant breeds can take up to 16 months to reach their full size, whereas small breeds can be full-grown by eight months. The main downside is that the calculator doesn't take into account health and feeding considerations.

Final Thoughts

Adopting a puppy is a big commitment that needs preparation since you're welcoming a furry family member for life. For instance, you bring home your adorable 8-week-old Great Dane pup, only to realize a few months down the line that he's unexpectedly the size of a small pony.

That's why you need to know the expected adult size so you can plan and prepare on how to accommodate your furry friend throughout his life. Simply use the weight calculator to get the estimates. Then, consider the above factors to determine whether the dog will be larger or smaller than the calculated estimates.