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How Big Do Maine Coons Get, and When Do They Stop Growing?
How big a full grown Maine Coon gets by the registry's figures, when it stops growing, how long Maine Coons live, and what the size means for gear.
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A full grown Maine Coon is one of the biggest house cats: the Cat Fanciers’ Association (CFA) says a mature male can reach or exceed 20 pounds, with females usually smaller. Maine Coons grow slowly and can take up to three years to reach full size, so a one-year-old still has growing to do.
CFA calls the breed “the largest of all pedigreed cats.” That does not mean every Maine Coon is huge. The registry gives no minimum, no female range and no growth chart, and any chart you find online that promises a weight at a given month is not from the breed’s registry. What the standard does describe is the shape, which matters as much as the weight when you buy gear.
What makes a Maine Coon look so big
The CFA standard describes a “muscular, broad-chested” cat with a “well-balanced rectangular appearance.” Several features add to the impression of size:
- Length. The body is rectangular rather than compact, and the tail is “long, wide at base, and tapering.”
- Coat. The coat is “heavy and shaggy,” shorter on the shoulders and longer on the stomach and back legs, ending in “a dramatically long plumed tail.”
- Paws and ears. Paws are “large, round, well-tufted,” and the ears are “large, well-tufted, wide at base.”
A cat that is long as well as heavy needs room to turn in a litter box and to lie flat on a perch. That is the practical difference between a Maine Coon and an average house cat.
When does a Maine Coon stop growing?
The registry calls the Maine Coon “a slow-maturing breed that can take up to three years to reach full growth.” The 2021 AAHA nutrition guidelines put most cats at skeletal maturity around one year of age, so this is the point owners notice most: the cat keeps filling out through its second and third year.
That timeline is the reason to size up early. If you buy a litter box, carrier or harness for a young Maine Coon, choose sizes with room to spare, or expect to replace them.
| Life stage | What the registry or study says | What it means for gear |
|---|---|---|
| First year | Still growing; no registry growth chart | Buy adult-size boxes and trees now |
| Up to 3 years | “Up to three years to reach full growth” (CFA) | Recheck harness and carrier fit |
| Adult | Males can reach or exceed 20 lb (CFA) | Check maker weight limits on trees and perches |
| Older cat | Joint and heart questions come up (see care) | Low-entry boxes, ramps, vet checks |
How long do Maine Coons live?
The best figure we found comes from a 2024 study in the Journal of Feline Medicine and Surgery that built life tables from UK veterinary records. It estimated a life expectancy at birth of 9.71 years for Maine Coons, with a 95% confidence range of 8.42 to 11.00 years, based on 69 deaths. For comparison, the same study gave 11.74 years for cats overall and 10.31 years for Ragdolls.
Treat those numbers with care. They describe a population in one country, the Maine Coon sample is small, and the range is wide. The study also found that lifespan dropped as adult weight moved away from the median for the cat’s breed and sex, in either direction. Keeping a big cat at a healthy body condition matters; our page on heart and hip health in large breeds covers the conditions vets screen for.
What the size means at home
The gear that most often needs replacing as a Maine Coon grows:
- The litter box. Box size is set by body length. See litter boxes for large cats for the sizing rule from veterinary behavior guidelines.
- The cat tree. A 20-pound cat jumping onto a top perch puts real force on the base. See cat trees for large cats.
- The carrier. A carrier has to let the cat stand and turn around. See carriers for large cats.
Extra large litter boxes for a full grown Maine Coon
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How a Maine Coon compares with other big breeds
The Ragdoll matches the Maine Coon’s top weight in CFA’s descriptions, and the RagaMuffin comes close. The Norwegian Forest Cat, which looks similar, is lighter by the registry’s figures (12 to 16 pounds for males). The large breeds hub has the full size table, and the Maine Coon vs Norwegian Forest Cat page explains how to tell the two apart.
Grooming is the other daily consequence of the size: a long, heavy coat on a big cat is a lot of fur. The Maine Coon grooming guide covers brushing, mats and nails.
Carriers with room for a 20-pound cat
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Frequently asked questions
How big is a full grown Maine Coon?
The Cat Fanciers' Association says a mature male can reach or exceed 20 pounds and that females are usually smaller. The breed is long and rectangular with a heavy coat and a long plumed tail, so it looks larger than its weight.
When do Maine Coons stop growing?
The registry describes the Maine Coon as a slow-maturing breed that can take up to three years to reach full growth. Plan gear for the adult size rather than the size at one year.
How long do Maine Coons live?
A 2024 study of UK veterinary records estimated a life expectancy at birth of 9.71 years for Maine Coons, with a confidence range of 8.42 to 11.00 years, against 11.74 years for cats overall. Many individual cats live longer; ask your vet about your own cat.
Is a Maine Coon a good house pet?
The registry describes Maine Coons as gentle, easy going yet active, friendly, sweet-tempered and easy to train. Their size means they need bigger litter boxes, sturdier trees and larger carriers than most cats.
Sources
- 2021 AAHA Nutrition and Weight Management Guidelines for Dogs and CatsAmerican Animal Hospital Association (JAAHA), hosted by the Canadian Veterinary Medical Association
- Maine Coon CatThe Cat Fanciers' Association
- Maine Coon Cat (breed standard)The Cat Fanciers' Association
- Life tables of annual life expectancy and risk factors for mortality in cats in the UK (Teng, Brodbelt, Church and O'Neill, 2024)Journal of Feline Medicine and Surgery, via PubMed Central
Filed under BreedsStart with Large Cat Breeds: Which Grow Biggest and How Big They Get
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