If you have recently adopted a St Bernard puppy or are thinking of doing so, you might be wondering about St Bernard size and just how big they will get. Spoiler Alert – the answer is pretty darn big! Looking for precise details? Keep reading for info on the St B’s height and weight, their growth rates, and more. Then tap your pup’s details into our handy Puppy Growth Calculator for a guestimate of their adult size.
Probably the best known of the giant dog breeds, Saint Bernard’s are legendary. Their search and rescue dog role high up in snowy mountain peaks has had them hailed as heroes since day one. However, these gentle giants also make great family pets for those with plenty of space to house them.
Our handy interactive puppy growth chart and calculator takes all the hard work out of predicting your puppy’s potential adult size. This helps you to know exactly what you are in for.
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St Bernard Size Predictions by Age
Kind, gentle, intelligent, St Bernards have traditionally been used as working animals because of their strength and trainability. However, their popularity as pets surged in the 1990s because of THAT musically-named movie. Despite the star’s portrayal as a bit of a cheeky chap, St Bernards are, in actuality, calm and placid pups. Their size is intimidating, but their demeanor is very definitely not!
However, for all their excellent qualities, St Bs really do take some looking after. This is due mainly to that thick, weather-proof coat of theirs as well as their tendency to drool. If you’re a neat freak, then these are certainly not the pups for you! That being said, St Bernards are an excellent choice for a family pet. They love children and get on well with other dogs too.
The St B’s large size means that they do require a bigger home. However, their exercise needs are relatively modest. These dogs are prone to laziness, something that is common in larger pups. This could be an issue if their diet isn’t adequately controlled. You need to keep a close eye on their weight – make sure it’s within the standardized boundaries outlined below.
| Age | 3 months | 6 months | 1 year | Adult |
| Weight | 35 – 55 lbs | 65 – 100 lbs | 110 – 165 lbs | 120 – 180 lbs |
| Height | 8 – 12 inches | 16 – 18 inches | 26 – 30 inches | 26 – 30 inches |
*A dog’s height is measured from its withers – this is the point between the shoulder blades.
As you can see, these dogs grow incredibly fast in the first 6 months of their lives. Sometimes it may even seem like you can actually see them growing; it happens so quickly. After this first half-year, though, the growing will slow, and then it will slow again once they get past their first birthday.
Are There Different Sizes of St Bernard?
St Bernards have been around for quite a while now, which means their size is fairly standardized. You shouldn’t see all that much variation, although the size of your pup’s parents could have an impact on whether they are at the smaller or larger end of the scale.
As with most larger breeds, there can also be quite a substantial gender difference in height and weight. Male dogs tend to sit between 28 to 30 inches and weigh in at 140 to 180 pounds. Female dogs are often on the smaller side at 26 to 28 inches and 120 to 140 pounds. However, both males and females are large and sturdily built with plenty of muscle, as is common to this breed.
More recently, to match the demand for these gorgeous dogs but at a more manageable size, breeders have started working on Mini and even Micro St Bernards. However, to achieve this smaller size (Mini – 15 to 20 inches and 40 to 60 pounds, Micro – under 15 inches and 15 to 35 pounds), a St Bernard is mixed with a Cocker Spaniel. This means that these dogs aren’t, strictly speaking, St Bernards at all. Though they do usually have the look of them.
St Bernard Growth Patterns
St Bernards really do shoot up quickly! By the time they are 8 months old, they will already be at 75% or more of their adult height. At this point, they will very much look like the lanky puppies they still are as muscle takes longer to develop. They will need much more time to fill out.
When a Saint Bernard turns one, they will likely have achieved their full height. They won’t be far off their adult weight either. However, some dogs can keep putting on weight right up to their second year and even beyond that. Don’t be surprised if that is the case with your hound – especially if their parents are pretty big, if they are working animals or getting more than average amounts of exercise.
Additionally, this is why it’s particularly important that your Saint Bernard puppy gets the correct nourishment he needs to grow that adorable little body into a healthy adult one. Check out these guides on best dog food for puppies here.
How Big is a Full-Grown St Bernard?
At their final size, a St Bernard will be somewhere between 26 and 30 inches in height and will weigh around 120 to 180 pounds. Males will be on the higher end of the scale (28 to 30 inches and 140 to 180 pounds) and females on the lower end (26 to 28 inches and 120 to 140 pounds). Larger male dogs could even break through the 200 pounds mark.
To predict your St Bernard’s adult size, factor in that they usually get to half their total weight around 5 to 6 months and their adult size at roughly 24 months.
You can calculate their potential adult weight at 23 weeks by taking what they weigh at that age and multiplying it by two.
A different formula you could use is:
- Growth = current weight / current age in weeks
- Adult weight = Growth x 52 (number of weeks in one year)
So, for example, if your 12-week old pup weighs 18 pounds. You simply divide the current weight by their age in weeks and multiply the result with 52:
18/ 12 = 1.5
1.5 x 52= 78 pounds
78 pounds would be the expected weight of your adult-sized Saint Bernard.
What Age is a St Bernard Fully Grown By?
Naturally, larger dogs take a little longer to achieve their adult height and weight. St Bernards, as a ‘giant’ breed, aren’t considered to have reached their mature size until they are 24 months or two years old. However, they will more than likely be at their final height and close to their adult weight a full year before that. Even though they are fully grown physically by this age, these dogs tend to hang on to their puppy-like ways well into their third and even fourth year.
If you’ve decided you’re up to the challenge of a giant dog and have taken on a St Bernard, you are going to want to be a prepared as you can. Knowing what to expect in terms of their growth rate and adult size is a vital part of this. It can help you get the right kind of accessories, plan their diet, and so much more.
Luckily, as Saint Bernards have been around for quite a while, the information on them is pretty accurate. So you should have a much clearer understanding of how big you might expect your St B puppy to get and when after reading this article.
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