When is a Great Dane fully grown?
Most Great Danes reach close to their adult height by around 18 months, but as one of the largest dog breeds, they typically keep filling out in weight, chest depth and muscle for considerably longer, often not looking fully mature until somewhere between two and three years old. Their sheer size means the growing process takes noticeably longer than it does for a small or medium breed.
Why giant breeds take so long to mature
A Great Dane can go from a few kilos at birth to an adult weight of 50-90kg or more, which is an enormous amount of growth to pack in even over an extended timeline. Giant breeds are generally advised to grow at a controlled, steady rate rather than as quickly as possible, since rapid growth puts extra strain on developing joints and bones during the period they're carrying the most rapidly increasing weight.
This is one of the main reasons large and giant breed puppy foods exist as their own category, formulated with a different calcium and calorie balance than a standard puppy formula, aimed at supporting steadier bone and joint development rather than the fastest possible growth.
What actually happens at different stages
Height growth is generally the first thing to level off, with many Great Danes close to their adult height by 12-18 months even though they still look lean and unfilled at that point. Weight, chest depth and overall muscle mass continue developing well beyond that, which is why a Dane can look noticeably different at 18 months compared with two or three years old.
Growth plates in giant breeds also close later than in smaller dogs, generally not fully closing until somewhere around 18-24 months, which is part of why vets often advise caution with high-impact exercise, long runs and jumping until a young giant breed dog is more mature.
When to involve a vet
A Great Dane growing unusually fast, developing lameness, or showing an odd gait during the rapid growth phase is worth having checked by a vet promptly, since giant breeds carry a higher risk of certain developmental joint conditions during this period than smaller dogs do.
If you're ever unsure whether your Dane's rate of growth and current condition look appropriate for their age, a vet can assess them properly at a routine visit, which is more reliable than judging purely against a general timeline.
Common questions
- How much does a fully grown Great Dane weigh?
- Adult Great Danes typically weigh somewhere between 50kg and 90kg, with males generally heavier than females and plenty of individual variation either side of that depending on line and build.
- At what age should I switch my Great Dane from puppy to adult food?
- This depends on the specific food's guidance and your dog's individual growth, so it's worth checking the packaging of whatever large or giant breed puppy formula you're using and discussing timing with a vet, particularly given how long giant breeds keep developing.
- Is it normal for a Great Dane puppy to look lanky or unbalanced while growing?
- Yes, giant breed puppies commonly go through gangly phases where legs, chest and head seem to grow at different rates. This is a normal part of their extended growth period and typically evens out as they mature.
- Should I limit exercise for a growing Great Dane?
- Many vets recommend avoiding high-impact activity such as jumping, long runs or repetitive stairs until a giant breed's growth plates have closed, generally well into their second year. A vet can advise on what's appropriate for your individual dog's age and development.
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Written against guidance published by UK veterinary and welfare organisations. Always confirm specifics with your own vet.
Written by Matt Garnett, who runs Giddy Pets and is a lifelong pet owner — not a vet. This is general information, not veterinary advice, and it cannot replace an examination by the vet who knows your animal. How we write these guides.