• Up to three or four months, a kitten is easiest to weigh on kitchen scales accurate to the gram: put it in a bowl or box and subtract the container's weight. An older kitten won't stay on kitchen scales, so step on the bathroom scales first on your own, then holding the kitten, and work out the difference.
• Weigh at the same time of day, ideally in the morning before feeding. A big meal adds tens of grams, and the line on the chart starts to jump about.
• Kittens are weighed every day for the first two weeks of life, then once a week until six months, then once a month. An adult cat only needs weighing every few months and before a vet visit.
• The calculator keeps your weigh-ins in this browser. To open them on another device or show them to your vet, copy the link to the chart.

Maine Coons take a long time to grow: fastest in the first year, then more slowly, reaching their final weight at three to four years. Kittens from one litter can be a couple of kilos apart by their first birthday, and the biggest kitten at two months won't necessarily be the biggest adult. So a kitten's weight can't honestly tell you what the adult cat will weigh.

What a few weigh-ins do show clearly is how it's growing. A healthy kitten usually keeps to its own lane within the range: if it started near the bottom edge and grows along it, that's normal. What should worry you is something else: the weight stops going up, drops, or the line jumps from one edge of the range to the other within a month or two.

The range on the chart is approximate. There's no scientific growth curve specifically for Maine Coons, so it's been put together from cattery tables and breed reference books and will be refined. There's more about the stages of growth in Maine Coon growth and nutrition.

A Maine Coon's coat is thick, so you can't tell by eye whether it's thin or overweight. Check with your hands.

• Ribs. Run your palms along the sides. Normally you can easily feel the ribs under a thin layer of fat, but they don't stick out. If you have to press to find them, the cat is on the plump side. If every rib feels sharp and you can see the spine, the cat is too thin.
• Waist. Look from above with the coat wet or smoothed down: there should be a visible waist behind the ribs.
• Tummy. A flap of skin low on the belly that swings as the cat walks is common in Maine Coons, slim ones included. It isn't fat. Fat feels like a firm layer on the sides, back and base of the tail.

Vets assess this on a body condition scale, usually with nine points and normal in the middle. Ask your vet at the next check-up where your cat is on it. How much to feed at different ages is covered in How much to feed a Maine Coon.

• A kitten has lost weight, or hasn't gained any for two weeks running.
• An adult cat that isn't on a diet has lost a tenth of its weight or more.
• The weight change comes with other signs: the cat eats less, or eats more than usual and still loses weight, drinks a lot, has become lethargic, or has vomiting or diarrhoea.
• The cat has put on noticeable weight and you can no longer feel the ribs.

The calculator doesn't diagnose anything and is no substitute for a vet's examination. It helps you keep records and notice in time if growth goes off track. If your kitten is from our cattery, send us the chart: we like to see how our kittens are growing. Our kittens.