It depends. A dog's size is dictated by many factors, from breed to diet. Some dog breeds are naturally small, while others are big. Some dogs can go beyond their typical size just because of overfeeding. 

If you want to get a dog, there are many considerations to make. For instance, you want to know what dogs eat, their sleeping arrangements, and exercise needs. If you are getting a puppy, you’ll also be concerned about how big he/she will get. Your dog’s size is important because it dictates many things from the space needed to how much food he’ll eat. You can be able to plan better for your dog's future if you know how big he'll get.

It can be costly if your dog keeps outgrowing his crate or kennel. To avoid such problems, it’s important to understand the factors affecting a dog’s size.

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• Factors
• What if your dog isn't a purebred?
• Other ways to determine your dogs adult size
• Calculating the size of giant breeds
• Calculating the size of medium-sized breeds
• Calculating the size of small breeds
• Summary

Factors That Influence A Dog's Size

Breed: The answer to the question lies largely on breed. As mentioned above, there are large and small breed dogs. Large dog breeds like Leonbergers grow up to a height of 65 to 75 cm (for males) and 72 to 80 cm (for females). The average weight of adult Leonbergers is 41 to 59 kg for females and 48 to 75 kg for males.

If you have a Leonberger, you can expect his/her size to fall within this range. While it's possible for dog breeds to grow beyond the expected range, Leonbergers can surpass the above AKC size range because of overeating. On the other hand, your Leonberger puppy may fall below the average size if you don't feed him/her high-quality dog food.

In a nutshell, you can’t expect to see a giant Chihuahua or a miniature Leonberger. However, while most dogs will grow to a size that corresponds with the breed, other factors like diet can come into play.

Gender: Generally, female dogs tend to be smaller than their male counterparts of the same age. This is precisely why size guidelines for dogs are given for each gender. To determine the size your puppy will get, start by knowing his breed then gender.

Age: Breed and gender aside, your dog’s age will also dictate his size. While all puppies, regardless of breed, tend to be small, their size will start to differ as they age. Small breeds tend to reach adult size in a short time (as early as 6 months). Large dog breeds can take 18 to 24 months to reach adult size. So, if you have a 6 month old puppy belonging to a large dog breed, he has a year to 1.5 years to reach adult size.

Exercise: The environment and activity also play a role in determining your dog's adult size. While exercise is highly recommended for puppies to increase their bone density, too much exercise can damage your dog's ligaments and/or skeleton, slowing down or stopping growth in severe cases.

Nutrition: A puppy from a large dog breed may fail to realize their adult size because of poor nutrition. Puppies need their mom's milk to develop fully. Lack of milk or a substitute formula can hinder your puppy's growth significantly. Weaning should be complemented with high-quality dog food that matches your puppy's life stage if you want proper growth.

Litter size: How many siblings does your puppy have? Larger litters tend to produce smaller puppies for obvious reasons. Since puppies need their mother’s milk to grow, larger litters tend to have “strained resources”. If your puppy didn’t have enough milk, he/she will probably be smaller than the average size of their breed when they reach adulthood. To have an accurate prediction, you should research the average litter size of your dog's breed to know if they were part of a small, normal, or large litter.

Other factors: Your dog’s growth can also be altered by factors like desexing. Spaying or desexing female dogs, which involves the removal of ovaries and uterus, can make dogs bigger. The same applies to neutering for male dogs. These standard surgical procedures can "cancel out" the chemicals responsible for "telling" the bones of your dog to stop growing. As a result, early neutering almost always results in longer bones/taller dogs.

What If Your Dog Isn’t A Purebred?

If your dog is a mix of different dog breeds, you may have a harder time determining how big he/she may get. There is less guesswork involved when dealing with purebred puppies. If you happen to rescue a puppy and you’re trying to determine how big he may get, here’s what you should do.

Check The Paws

Puppies with large feet have a lot of “room” to grow. You just need to look at your dog’s paws to see if they look proportional to the rest of the body. However, you shouldn’t focus on this alone.

Track Your Dog’s Weight

You can also consider weight. Typical newborn puppies grow up to double in body weight within a week. Afterwards, they gain anything from 5 to 10% of their body weight on a daily basis. After 6 weeks, small breeds tend to gain approximately 5 pounds a week while their larger counterparts gain weight slower. With this information alone, you can be able to estimate the age of your dog and how long he has left to grow.

As mentioned above, large dogs will be fully grown within 24 months. Small dogs can reach adult weight in 6 months. The weight landmark to watch out for is 6 months. By this time, small dogs are usually two-thirds of their adult weight, if not more. Large dogs are usually half their weight at this age.

Other Ways To Determine Your Dog’s Adult Size 

You can consider alternative methods to estimate their ideal size. There are general formulas to consider that work for both small and larger dogs. 

Puppy’s weight ÷ age in weeks x 52 = The puppy’s expected adult weight

If you adopt a puppy from a shelter, predicting their size can be a daunting task if you can’t tell the breed. A simple DNA test can reveal the puppy’s breed. If they are a mixed breed, you can tell the breed/s of the parents.

Vets just need a blood sample to trace the breed of origin. The process can take some time. If waiting for the results of such a process doesn't make sense for many reasons i.e., the rate at which your dog is growing, you can consider other factors.

Skin

You can predict your dog's adult size accurately by looking at their skin. Puppies tend to have loose skin. If that's the case with your dog, he/she has "room" for growth. The extent of growth can be dictated by how loose the skin is. Large saggy skin "bags" indicate that he has more room for growth in the future. Small loose skin indicates that he/she may be near adult size. Small dog breeds also have small loose skin. While this tip may be accurate, it isn't foolproof. Overweight adult dogs also tend to have loose skin. As a result, you shouldn't rely on the looseness of the skin alone.

Height Of The Dog's Parents

If you are adopting a puppy and you have access to the parents, you can predict their size by simply looking at how big the parents are. Female dogs tend to carry dominant genes. If your puppy’s mother is larger than the father, the puppy is more likely to take after the mother’s size. While DNA structure can dictate size, the dominant genes usually dictate the size of a mixed puppy.

Calculating The Size Of Giant Breeds

How big will my dog get if he is a member of a larger breed (such as a Great Dane)?

Giant breeds take 12 to 36 months to reach adult size. However, the most rapid growth will occur between 0 to 25 weeks. To calculate the average size, divide the dog's weight at 5 months by their age in weeks, and multiply by 52 weeks.

A giant breed puppy weighing 50 pounds at 20 weeks will weigh 130 pounds i.e., 50 divided by 20 times 52 weeks. The same applies to large dog breeds. To get their adult size at six months, just double their weight.

Calculating The Size Of Medium-Sized Dog Breeds

Medium-sized dog breeds should reach adult weight in 9 to 12 months. The most rapid growth occurs between 0 to 4 months. To calculate the size of a medium-sized breed, multiply their weight at fourteen weeks, double that and add to half their weight at 14 weeks.

For a puppy weighing 13 pounds at fourteen weeks their adult size will be: 13 x 2 = 26, 26+6.5=32.5 pounds.

Calculating The Size Of Small Dog Breeds

Small breeds stop growing anywhere from 8 months to a year. They have growth patterns that match those of toy breeds i.e., most growth occurs between zero and eleven weeks. During this period, small breeds gain 5 to 8 ounces every week. Toy breeds grow 1 to 5 pounds per week.

A small breed dog or toy breed weighing 3 pounds at 1.5 months will weigh 3 x 2 = 6, 6 x 2 = 12 pounds. (double their weight twice)

Summary

It depends. As seen above, many factors will determine how big your dog can get. Hopefully, you now have a good idea of how big your dog will get even if you don’t know their breed or you can’t tell their age. You can check AKC's breed-weight Chart for size details in regards to gender.

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