Four breeds account for most genuine size in cats: the Maine Coon, the Ragdoll, the Norwegian Forest Cat and the Siberian. None of them is defined by weight, and a large unregistered domestic cat reaches the same numbers routinely. What separates them is muzzle shape, head outline and coat structure, in that order.
Which means the question people usually ask, “how heavy does my cat have to be for it to be a Maine Coon,” has no useful answer. The better question is what the standards actually measure.
Why is weight the worst feature to judge on?
Because it moves with age, and the registries barely use it.
Campigotto and colleagues published the largest look at this in the Journal of the American Veterinary Medical Association in 2019, working from the electronic medical records of 19,015,888 cats seen at clinics in the United States and Canada. For the four most common recognized breeds in that data, Siamese, Persian, Himalayan and Maine Coon, mean body weight peaked between six and ten years of age and then declined. For domestic shorthair, medium hair and longhair cats, mean weight peaked at eight years.
So a cat’s weight tells you roughly how old it is and something about its history. It does not tell you what it is. A three-year-old Maine Coon and an eight-year-old domestic shorthair can sit at the same number on the same scale, and the shorthair will often win.
One more detail from that study is worth knowing before you compare your cat to anything on the internet: the authors report that 9,886,899 of 19,015,888 cats, 52 percent, had only one body weight on record. Most cats are weighed once. Population averages built from that are honest, but they are not a growth chart for your cat.
What do the standards actually say about size?
Less than you would expect, and in some cases the opposite of what the listicles repeat.
Maine Coon. CFA does not set a numeric weight in the standard text. The profile notes that males commonly reach or exceed 20 pounds and that females are usually smaller, and it adds the line that matters most: “This is a slow-maturing breed that can take up to three years to reach full growth.” The body is required to be “muscular, broad-chested,” size “medium to large,” and “long with all parts in proportion to create a well-balanced rectangular appearance.”
Ragdoll. Also large. CFA calls for a body “large and long, broad and solid, with heavy boning,” rectangular in shape, with males reaching or exceeding 20 pounds and full size arriving at around four years.
Norwegian Forest Cat. Smaller on paper than its reputation. CFA gives males 12 to 16 pounds and females 9 to 12 pounds, reached at roughly five years.
Siberian. Smaller still by the book: males 12 to 18 pounds, females 8 to 12 pounds, on a body “medium in length, and well muscled with the back arched slightly higher than the shoulders, with a barrel-shaped, firm belly.”
Read those four together and the picture flips. A 17 pound cat is inside the published range for a Siberian, above the published range for a Norwegian Forest Cat, and unremarkable for a well-grown domestic cat of eight years. Size on its own puts nothing in or out.
Which features actually separate them?
The standards are unusually explicit here, and they separate on the head first.
The muzzle. The Maine Coon’s must be “visibly square, medium in length and blunt ended when viewed in profile.” The Norwegian Forest Cat’s disqualification list names a square muzzle, which is to say the single feature the Maine Coon requires is the feature that would remove a Norwegian Forest Cat from the bench. The Siberian narrows “slightly to a full-rounded muzzle.” Three breeds, three different answers, all visible in one profile photograph.
The head outline, seen straight on. Maine Coon: “medium in width and slightly longer in length than width with a squareness to the muzzle.” Norwegian Forest Cat: an “equilateral triangle, where all sides are of equal length as measured from the outside of the base of the ear to the point of the chin.” Siberian: a “modified wedge of medium/large size with rounded contours.” Rectangle, triangle, rounded wedge.
The body outline. The Maine Coon wants a rectangle. The Norwegian Forest Cat disqualifies a “long rectangular body” and asks for one “moderate in length.” The two breeds are so close in coat and size that the standards had to draw the line somewhere else, and they drew it here. The Maine Coon versus Norwegian Forest Cat comparison takes that pair feature by feature.
The coat. Maine Coon: “heavy and shaggy; shorter on the shoulders and longer on the stomach and britches,” silky and falling smoothly. Norwegian Forest Cat: a “distinguishing double coat, consisting of a dense undercoat, covered by long, glossy and smooth water-resistant guard hairs.” Siberian: a triple coat, with an abundant full collar ruff and hair that may thicken to curls on the belly and britches. Uneven and shaggy, water-resistant and double, or dense and triple. That is a texture question, and it is readable in a close photograph of the flank.
The ears. Maine Coon: “large, well-tufted, wide at base, tapering to appear pointed,” set about one ear’s width apart. Norwegian Forest Cat: “medium to large, rounded at the tip, broad at base,” heavily furnished, with lynx tips desirable but not required. Pointed versus rounded is a real distinction, and the tufts that everyone photographs are common to both. For more on ears as an identifying feature, see cat breeds with big ears.
So is your big cat a Maine Coon?
Probably not, and the reason is definitional rather than statistical. Pedigree is a registry record, so a large longhaired cat with no papers is a domestic longhair that grew well, whatever it resembles, and the domestic shorthair page covers what those terms do and do not commit to. That is not a downgrade. The traits people fall in love with, the ruff, the plumed tail, the ear tufts and the size, all exist in unregistered cats, because those cats share the same ancestry the breeds were built from.
The honest test is whether the features agree with each other. A square blunt muzzle, a rectangular body, uneven shaggy coat and large pointed ears pointing the same way is a real resemblance worth taking seriously. A big fluffy cat with a rounded wedge head and a barrel body resembles a Siberian more than a Maine Coon, and a big fluffy cat whose features scatter is simply a big fluffy cat.
Photograph your cat straight on and in profile, in daylight, standing if it will cooperate. Cat Identifier reads those two frames and returns the breeds your cat most resembles as a percentage mix, with the traits behind each match. It reads visible likeness rather than ancestry, and only registration papers from a registry establish pedigree. To check the Maine Coon case specifically, is my cat a Maine Coon walks the standard trait by trait, and what breed is my cat covers the general sorting.
The short version
Stop weighing the cat. Look at the muzzle in profile, then the head outline straight on, then the coat structure, then the ears. Those four are what the registries wrote down, they are what a photo can carry, and they are the only part of this question that a number on a scale was never going to answer.
Sources
- Maine Coon Cat breed profile and show standard, The Cat Fanciers' Association
- Norwegian Forest Cat breed profile and show standard, The Cat Fanciers' Association
- Siberian breed profile and show standard, The Cat Fanciers' Association
- Ragdoll breed profile and show standard, The Cat Fanciers' Association
- Campigotto et al., Investigation of relationships between body weight and age among domestic cats stratified by breed and sex, JAVMA 255(2), 2019