Bullmastiff Growth Chart By Month

If you are looking at a Bullmastiff puppy who already outweighs the family cat and wondering where this is all heading, you are asking the right question at the right time. The Bullmastiff is a genuine giant, and the first two years shape the calm, powerful adult your puppy becomes. This guide gives you a clear month by month weight picture, an honest timeline for when growth finishes, and the everyday habits that help your Bullmastiff carry all that substance with ease.

How much should a Bullmastiff weigh by month?

A fully grown male Bullmastiff usually weighs 110 to 130 pounds and stands 25 to 27 inches at the shoulder. Females typically weigh 100 to 120 pounds and stand 24 to 26 inches. Growth is fastest between two and six months, when a puppy can gain 8 to 12 pounds in a month, then slows through the first year. Most of the height arrives by 12 to 15 months, while width and depth build until two and a half to three years.

Genetics, sex, line and nutrition all shape the final number, so treat these ranges as a dependable guide rather than a rule. With a breed this heavy, how your Bullmastiff arrives at adult size matters far more than the number itself. Slow and even beats big and fast.

What makes a Bullmastiff grow the way it does

The Bullmastiff was created in England as a gamekeeper dog, bred to be quick enough to catch a poacher and steady enough to hold rather than harm. That job called for a blend of English Mastiff substance and Bulldog agility, and you can still see both halves in a growing puppy: enormous bone and muscle packed onto a compact, square frame.

That density is exactly why the growth years deserve attention. A Bullmastiff puppy is carrying a giant breed load on a body that is still assembling itself. Through the middle of the first year many look oddly proportioned, with a broad head and heavy paws attached to a body that has not caught up yet, and some go through a leggy phase before widening dramatically in the second year. All of that is normal.

Bullmastiffs are also not endurance athletes. The short muzzle and heavy build mean they warm up quickly and tire sooner than a working breed of the same size, so a growing puppy needs regular gentle movement rather than long sessions.

Bullmastiff growth chart, month by month

Use this chart as a friendly guide rather than a report card. A puppy who tracks a little above or below these ranges while looking lean is usually doing just fine.

Bullmastiff Growth Chart By Month: reference table

Age	Male weight	Female weight
2 months	22 to 30 lb	18 to 26 lb
3 months	35 to 45 lb	30 to 40 lb
4 months	50 to 62 lb	45 to 55 lb
6 months	75 to 90 lb	65 to 80 lb
9 months	93 to 110 lb	83 to 98 lb
12 months	100 to 120 lb	90 to 108 lb
18 months	105 to 128 lb	95 to 115 lb
2 years plus	110 to 130 lb	100 to 120 lb

When do Bullmastiffs stop growing?

Bullmastiffs reach most of their adult height between 12 and 15 months. From there the change is all about substance. Your dog broadens through the chest and shoulders, the head deepens, and the outline becomes the blocky shape the breed is known for. That process usually runs until two and a half to three years of age, so a rangy fifteen month old is right on schedule.

As a rough guide, dogs with an expected adult weight of 100 to 130 pounds keep developing their frame for roughly 22 to 26 months, with muscle and width filling in beyond that. Because the skeleton is largely set in that stretch, this is your prime window to build strong habits around food, movement and joint support.

Why the growth window matters so much for a giant breed

During this window your Bullmastiff is laying down the cartilage, bone and connective tissue that will carry well over a hundred pounds for the rest of its life. Growth plates, the soft areas at the ends of the long bones, stay open through much of the first year and close later in giant breeds than in smaller dogs. While they are open, extra weight and hard impact ask a great deal of a frame that is still forming, which is why lean feeding and moderate exercise matter so much for this breed.

How much should a Bullmastiff eat while growing?

Giant breed puppies do best with steady, moderate growth. An even curve supports comfortable movement now and for years to come, and with a Bullmastiff it also keeps a very heavy adult from arriving before the frame is ready. A few practical habits make a real difference:

• Choose a complete food formulated for large breed puppies, which balances calories, calcium and phosphorus for slower, steadier growth.
• Split the daily amount into three meals while young, then two meals as an adult, so energy stays even and each meal stays modest.
• Resist the urge to feed for size. A Bullmastiff will get big on its own schedule, and rushing it does the frame no favours.
• Feed to a lean body condition, and count training treats in the daily total on a dog this food motivated.
• Ask your veterinarian to confirm the right daily amount at each checkup, since the correct portion changes quickly through the first year.

How to check body condition in ten seconds

The scale tells you weight, but body condition tells you whether that weight suits your dog. You can check it at home in seconds.

• Ribs. Run your hands along both sides. You should feel the ribs easily under a thin layer. If you have to press to find them, ease back on food.
• Waist. Look down from above. You want a clear waist that tucks in behind the ribs rather than a straight line from chest to hip.
• Tuck. From the side, the belly should rise gently toward the back legs rather than hanging level.

Check every couple of weeks through the growth years and adjust portions gently with your veterinarian to guide you.

Growth safe exercise for a Bullmastiff puppy

Bullmastiffs are surprisingly low key for their size and enjoy a walk and a sniff far more than a long run, which suits the growth years perfectly. Your aim is regular, moderate movement that builds muscle without pounding on a frame that is still forming.

• Favour short walks on soft ground and free play, letting your puppy set the pace.
• Keep jumping, hard sprints and repeated stair work moderate while the growth plates are still open.
• Break activity into several short outings across the day rather than one long session.
• Walk in the cool hours and stop early if breathing gets heavy, then let your puppy rest fully afterwards.

Protecting a heavy frame from the start

Every step a Bullmastiff takes travels through its joints, and there is a lot of dog above those joints. Supporting healthy joint development while the frame is still being built is one of the simplest habits a Dog Parent of a giant breed can adopt.

Alongside lean feeding and sensible movement, many big dog parents add a daily joint support chew made for large and giant breeds. MoveGuard Growth is built for exactly this stage. It combines nine actives, including 250mg New Zealand Green Lipped Mussel, 400mg glucosamine, 300mg chondroitin, MSM, krill oil and hyaluronic acid, to support the developing joints of young large breed dogs across the roughly 8 to 30 month growth window. You dose by expected adult weight, so almost every Bullmastiff sits at three chews a day. It is made in the USA, 90 chews to a jar, and is backed by a 60 day guarantee.

Signs your Bullmastiff is growing on track

You do not need a weekly weigh in to know things are going well. Look for a bright, settled puppy with a waist you can see from above, ribs you can feel with light pressure, easy movement, a good appetite and long stretches of deep sleep. Steady, unhurried growth is exactly the picture you want.

Signs worth a conversation with your veterinarian include limping, stiffness after rest, reluctance to rise or to climb into the car, or a sudden growth spurt. Catching those early means you can adjust food or activity while adjustments are still easy.

A simple growth game plan, stage by stage

You do not need a complicated programme to raise a sound Bullmastiff. You need the right emphasis at the right time.

8 weeks to 4 months. Foundation stage. Focus on a complete large breed puppy food, three calm meals a day, wide social exposure and short bursts of free play on soft ground. Start lead manners and gentle handling now, while your puppy still weighs less than you do. A Bullmastiff that learns early habits stays easy to live with at 120 pounds.

4 to 8 months. The fastest stretch. Weight can climb 8 to 12 pounds a month, so check body condition every couple of weeks and keep feeding lean. Set house rules around stairs, sofas and car entry, using a ramp rather than letting your puppy leap. This is a natural point to begin a daily joint support routine.

8 to 18 months. Height nears its ceiling while the body starts to broaden. Appetite can outpace need, so match portions to body condition rather than to enthusiasm. Build walks up gradually on forgiving surfaces, and keep training short and positive to channel a maturing mind.

18 months to 3 years. The rangy adolescent turns into the deep, blocky adult the breed is famous for, as width, chest and head substance continue to arrive. Increase activity as your veterinarian advises, keep the adult lean, and many parents carry a joint support routine into adulthood.

Common growth mistakes to avoid

Most growth trouble in giant breeds comes from a handful of avoidable habits. Steer clear of these and you are already ahead.

• Overfeeding for size. A heavy young Bullmastiff is not a healthier one. Feed lean and let size arrive on its own timeline.
• Skipping large breed puppy food. These formulas control calcium and calories for steady growth. Confirm the right food with your veterinarian.
• Underestimating the heat. A short muzzle on a heavy body is a poor cooling system, so warm afternoons and long sessions do not mix.
• Letting size do the training. Habits you tolerate at 40 pounds become immovable at 120. Teach manners while lifting your puppy is still possible.
• Waiting for a problem before supporting joints. The growth window is the ideal time to support developing joints, not after signs appear.

The Bullmastiff temperament and the growth years

For all the imposing looks, the Bullmastiff is a calm and deeply devoted family dog. This is a breed that wants to be near its people, often leaning against a leg or settling across a doorway, and one that is far more watchful than noisy. That steadiness is something you help shape during the growth years.

Bullmastiffs are independent thinkers with a stubborn streak, so short and positive sessions work far better than repetition or pressure. Five focused minutes a few times a day builds real understanding without boring a dog who dislikes being drilled. Social exposure matters just as much, because a puppy who meets many people, surfaces and situations grows into an adult who assesses calmly rather than reacting.

Bear in mind too that a Bullmastiff matures mentally about as slowly as it matures physically, so a two year old may still behave like an adolescent in a very large body. Build the mind and the frame together and you end up with the gentle, dependable guardian the breed is famous for.

Frequently asked questions

The bottom line

Your Bullmastiff will most likely mature into a 100 to 130 pound guardian who reaches adult height between 12 and 15 months and finishes filling out by two and a half to three years. Feed for lean, steady growth, keep movement gentle and frequent while those joints develop, respect the heat, support the growth window with the right daily habits, and train early while your puppy is still liftable. That is how you raise a Bullmastiff who carries all that substance with comfort and confidence.

Want the simple roadmap in one place? Grab our free Big Dog Growth Guide for the growth window checklist, feeding framework and joint safe exercise limits, all written for large and giant breeds.

This article is for general educational purposes only and is not veterinary advice. It is not intended to diagnose, treat, cure or prevent any disease. Always consult your veterinarian about your dog’s individual health, nutrition and supplement needs. These statements have not been evaluated by the Food and Drug Administration.