How Big Will My Puppy Get?

The size an adult dog will be is largely a function of breed and parental size and can be estimated from the puppy’s current weight when the size category is known. Toy breeds are finished at 8-10 months, medium breeds at 12-14 months, and giant breeds at 18-24 months.

The abbreviated version is that. The long version is more helpful as it really asks three questions: how big will my puppy get, how big will it be, and how long?

It’s the one question families ask most when waiting for a puppy and twice as common with a cross-breed since there is no one breed standard to refer to. So, let’s get this sorted out the correct way.

How Can I Tell How Big My Puppy Will Get?

There are 4 ways to determine how big your puppy will be: By the breed standard, by parent sizes, by a puppy weight estimate from the puppy’s age, and by taking them for a DNA test. Pedigree pups are most likely to be reliable when they come from a breed & parents. Weight based estimates are for all. Unknown mixes are filled with DNA.

Always begin with what you know! Pedigree puppies have a published breed standard and national kennels publish adult height and weight standards for all breeds recognized. The adult weight of a Labrador Retriever is approximately 25-36kg (or 55-80lb). The weight of a Cavalier King Charles Spaniel is 5.5 – 8kg (12 – 18 lb.).

Your puppy will come to rest within that band.

Parents further restrict it and for a cross-breed, it is more important than anything else. A puppy will not outgrow its parent’s size so if you meet mum and she is 20kg (44lb), expect the dog to be in the high teens to low 20’s.

With a deliberate cross, the two parent standards give you a bracket rather than a band. If you have a cross out of a 17kg (37lb) mum and a 23kg (51lb) dad, it is extremely unlikely that the puppy will be under 15kg or over 25kg at 10 weeks old regardless of what the puppy looks like. Don’t ask for the adult weight of the sire only, ask the parents.

No pedigree and no parents? If so, you will have to work from the dog’s weight and age, which we will discuss in the next section.

What is the Correct Weight of My Puppy at Each Age?

At about 4 months of age, puppies weigh about half their adult weight, and are about 5 to 6 months old when they are ½ the weight of their adult size when large and giant breeds. A medium or large puppy’s size at 16 weeks is a good guess at its adult size, if it is doubled. Triple the weight of a toy or a small puppy at 8 weeks does the same.

Almost all puppy growth charts are based on those two rules of thumb. They work because there is a fairly predictable growth curve within each size category and the greatest growth occurs from 8 weeks to 6 months.

A worked example is shown below: Bramble is a groodle, 8kg (17.6lb) at 16 weeks. Doubling yields 16kg (35lb). Her mum was a 17kg (37lb) Golden Retriever cross and dad a standard Poodle at around 23kg (51lb). When it comes to maths, the parents agree, so it is advisable to purchase the medium crate (16-22kg/35-48lb) rather than the small one.

If you don’t want to use the calculations, you can use a calculator that will run the same growth curve for you, but will allow you to estimate your puppy’s adult weight from its current age and weight. You select the size of breed (toy through to giant), enter the weight and age of the dog today and it gives you a reasonable range for its adult weight, instead of a single precision number. That’s the range you want as you’re a puppy, and puppies don’t read charts.

When Does a Puppy Stop Growing?

Between 8 months and 2 years of age, puppies will stop growing, depending on size. Toy breeds are 8-10 months of age, small breeds 10-12 months of age, medium 12-14 months, large 14-18 months and giant 18-24 months old.

Size category	Adult weight	Growth finishes
Toy	under 4kg (9lb)	8 to 10 months
Small	4 to 11kg (9 to 24lb)	10 to 12 months
Medium	11 to 25kg (24 to 55lb)	12 to 14 months
Large	25 to 45kg (55 to 100lb)	14 to 18 months
Giant	45kg+ (100lb+)	18 to 24 months

 

Height finishes first. Growth plates are the soft cartilage at the ends of the long bones and these harden and close at the end of that window and thereafter your dog will be as tall as he will ever be. This takes a couple more months until the frame becomes more filled with muscle and chest depth.

This causes confusion among big dogs. A Bernese Mountain Dog is a mature 12-month-old. It isn’t. It still has a year yet to broaden before it’s a full-fledged adult, not to mention a puppy skeletally, which means you shouldn’t do too much running and jumping with it, anyway.

Do Big Paws Mean a Big Dog?

On their own, large paws aren’t necessarily a good indicator of adult size. Puppies have cramped growth periods and sometimes paws, ears and legs will catch up with the body after a few weeks. Paw size is only a factor in concert with breed and parent size.

I know, everyone’s granny has a paw test. And in a sort of a way, a pup with feet the size of dinner plates isn’t likely to be a Chihuahua. However, I have witnessed 10-week-old spaniels grow into perfectly normal 14kg.

Use paws as a tie-breaker, NOT evidence.

What Else Changes How Big a Puppy Grows?

Sex, age at neutering and nutrition and health all influence a puppy’s ultimate size within its breed. Male dogs are 10-20% heavier than females of the same breed. Neutering before growth plates close gives a dog a slight increase in height and length, but not a decrease in size. Do not overfeed, as this will cause a puppy to become fatter, not bigger.

That’s a two-sentence statement, isn’t it? More food does not make a bigger frame! It will make a heavier puppy on the same bone structure and in large and giant breeds, the extra weight on still developing joints will increase the chances of hip and elbow issues later on. The concept of large breed puppy food is actually for this very reason; to slow down the growth rate so it matches the skeletons.

A puppy that is at least one month old and is not eating enough and/or sick during the first few months may be stunted in growth, but when corrected, a healthy, well-fed puppy will soon attain its genetic size.

What If My Puppy Is a Rescue or Unknown Mix?

If you are not aware of both of a puppy’s parents, use the weight estimate and then the size category that would be best suited for the puppy’s build, and then opt for a DNA test for greater assurance. In the UK, a DNA test will cost around £60 to £120, and will give breed mix and an estimate of the adult weight.

This is the decision structure I provide to owners.

Once you know the breed, refer to the breed standard and cease worrying. If you do know one parent, then use that parent’s size as your upper limit. If you don’t know either, weigh the puppy at 16 weeks and multiply that by 2 to get an approximation in the middle of a range that ranges about 20% on either side.

Now ask yourself one question that’s practical: Does the answer make any difference? If buying these 2 crates (or harness or car restraints) based on the difference between 18kg and 24kg (40lb and 53lb) means spending more money, then do it, but if it doesn’t, then don’t. If it does, store it for treats.

When Should I Worry About My Puppy’s Growth?

If a puppy does not seem to be gaining weight for two weeks or more before 6 months of age or if the puppy’s weight doesn’t seem to be on track to follow the growth curve, or the puppy has a very visible rib cage (no fat cover) it should be taken seriously. Take your time and take it slow, it’s okay. Stalled is not.

The scales are not the best check. It’s your hands. The PDSA guide to checking your dog’s body condition score takes you step by step: you should be able to feel the ribs with a light touch, see the waist from above and see the tummy tuck up from the side. If a puppy has passed those three checks and is gaining a bit per week, then that’s exactly what he should be doing.

If the puppy has not gained weight or if the weight gain has halted, schedule a veterinary consultation. The reasons for not growing quickly include a few less common conditions as well as worms and poor diet all of which can be corrected if they occur during the early growth stages.

But what if it was just that your puppy is growing more quickly than you had anticipated? Purchase the larger box. It’s something you needed anyway.