Your Maine Coon Could Keep Growing For Years: Here’s When It Finally Stops
Most cat breeds look fully grown by the end of their first year. This isn’t the case with Maine Coons, though! These felines don’t just grow big in kittenhood; they develop slowly, gaining muscle, bone mass, length, and coat fullness over several years.
If you’ve watched your Maine Coon steadily increase in size past their “kitten months”, you’re not imagining it.
This article dives deep into the growth pattern of Maine Coons: when their fastest growth happens, how long the slow build continues, what influences final size, and how you can best support your cat through every stage.
This topic is part of a broader look at how Maine Coons grow and develop, which is covered in our Maine Coon size and growth guide.
How Maine Coons Grow: The Timeline
Maine Coons mature much more gradually than many other domestic breeds. Their growth isn’t simply about height or weight; it involves bone development, muscle building, coat and mane fullness, and physical bulk.
Here’s how it typically unfolds:
Birth To ~6 months
During these early months, Maine Coons grow rapidly. They gain length, weight, and coordination quickly.
By six months, many will have reached a significant portion of their adult height or length, though not their full weight or muscle bulk.
6 To 12 Months
Growth continues strongly, though the pace slows somewhat.
Their bones are still forming, and much of their body shape, shoulder width, and chest depth are beginning to develop.
Some breeders and growth charts report that by 12 months, many Maine Coons may reach around 70-80% of their final weight, depending on their genetic lineage.
1 To 2 years
Though growth slows down after the first birthday, Maine Coons continue to fill out.
Muscle mass increases, bone structure solidifies, and their coat becomes fuller. Some males and females show slower but visible growth during this period.
2 To 3 years
Most Maine Coons have achieved the bulk of their adult size by this time, but that doesn’t mean growth stops. Many continue to gain in width, bulk (muscle and bone), tail length, and coat/mane thickness.
3 To 5 years
For many Maine Coons, full physical and coat maturation doesn’t happen until 3, 4, or even 5 years of age. This includes things like full mane development, muscular definition, and the final “weight plateau”.
Some sources report that males in some lines continue to fill out (add mass or body depth) right up to year 5.
This is when Maine Coons stop growing …
Growth Happens In Phases
Maine Coons don’t grow in a straight line. Most will gain height and length quickly in the first year, then continue filling out slowly as the chest broadens and muscle builds. This is why owners often think growth has “stopped” when it’s really just changed phase.
Factors Influencing When They Stop Growing
Not all Maine Coons grow at the same rate, nor do they end up the same size.
Several variables affect growth duration and final size:
- Genetics and Bloodline
Maine Coon kittens born to large parents (or from lines known for size) often grow larger and may take longer to reach full maturity. Breeding lines selected for height tend to produce cats that continue developing past 3 years. - Nutrition
What and how much they eat matters a great deal. High-quality, balanced diets with appropriate proteins, minerals, and calories in early life support healthy bone, muscle, and organ development. Undernutrition slows growth; overnutrition risks obesity, which can mask or distort healthy growth. - Health Status
Cats who suffer from early illness, parasites, or even silent issues like mild joint problems or dental pain may grow more slowly because energy is diverted to recovery rather than growth. - Gender
Males often grow larger than females, and in many cases may take longer to settle physically (in frame, muscle, build). - Spaying/Neutering Timing
Early or late spaying/neutering can affect the hormonal influence on growth plates. Some breeds show delays or small increases in final size if neutered after certain growth stages, though this is less dramatic than in some other animals. - Environment And Activity
A Maine Coon with plenty of room to move, climb, explore, and exercise will develop muscle and bone more fully than one kept mostly sedentary. Stimuli, stress, rest, and sleep also play roles.
When Can You Expect The “Finished” Look?
While individual variation is large, here are rough guidelines for when many Maine Coons begin to look “fully grown”:
- By 18-24 months, many will have much of their adult body shape. You’ll see a fuller chest, broader shoulders, more weight, and a more established coat.
- By 2-3 years, for many Maine Coons, further growth is less dramatic. The cat may still gain muscle mass (especially males), but visible changes will be subtler.
- By 4-5 years, most Maine Coons will have reached their “full package” – body size, mane, coat, structure. After this, changes are mainly weight, health, or seasonal coat thickness.
Keep in mind that in some exceptional cases, minor growth or “filling out” (bursting of mane, bulk in shoulder or chest) continues even beyond 5 years, though such cases are less common.
What “Fully Grown” Really Means
“Fully grown” usually means your Maine Coon has reached their adult frame and finished filling out with muscle.
Even when height and length slow down, many Maine Coons continue to mature in body shape, coat density, and overall bulk for much longer than the average cat.
Signs Your Maine Coon Is Near Adult Size
- Month-to-month weight gain becomes small and gradual
- Frame looks proportionate (less “gangly kitten” look)
- Chest and shoulders broaden
- Coat and ruff look denser and more adult-like
- Energy levels settle slightly (not always – temperament varies)
Warning Signs Growth May Be Problematic
Watching your Maine Coon grow is exciting, but there are signs that things might not be going smoothly:
- If growth is extremely slow, uneven, or your kitten seems disproportionately thin/lanky, it might be due to nutritional deficiency, illness, or genetic issues.
- Growth that stops abruptly early (before 2 years) while the cat seems healthy may mean growth plates closed early, or there was a health setback.
- Too rapid weight gain without proportionate bone or muscle development (i.e., looking overweight rather than growing in structure) can lead to joint or spine strain.
- Discrepancies between bone structure (chest, shoulders) and length/tail/limbs – for example, if legs remain very thin while body bulk increases drastically, this may suggest a lack of balanced nutrition or insufficient exercise.
How To Support Healthy Growth
To help your Maine Coon grow its best and healthiest, here are some detailed recommendations:
- Feed a high-quality diet appropriate for kittens and young cats: This includes high protein, balanced fats, and the necessary minerals for bone development (e.g., calcium, phosphorus).
- Avoid overfeeding: Measure food, monitor body condition (can you feel the ribs with light pressure? Is the waist shape present?), and avoid leaving food out all the time.
- Encourage consistent exercise: Climbing posts, interactive play with wand toys, or chase toys are good. Physical activity builds muscle that supports joints.
- Provide vet checkups regularly: Especially at critical growth stages (around 6 months, 1 year, 2 years) to monitor bone health, weight, and detect any underlying issues early.
- Maintain a stress-low environment: Stress, illness, or frequent disruptions during growth can divert energy away from healthy development.
Final Thoughts
Maine Coons are a breed defined by their slow, majestic growth. Unlike many cats that are essentially adult by one year, Maine Coons take 3-5 years (or more) to be fully mature – body, coat, bone structure, everything.
If you have a kitten or young Maine Coon, expect growth, changes, and refinement well into the third and even fourth year.
Watching them develop over time is part of the pleasure of owning such a breed. With attentive care, nutrition, exercise, and health, you can help ensure your Maine Coon matures into the strong, charismatic “gentle giant” they’re meant to be.
