A kitten should gain roughly 100 grams a week from 2 weeks to 4 months, and the whole curve can be checked at 3 points: 8 weeks, 16 weeks and 6 months. Weigh weekly on a kitchen scale, write the number down, and the scale tells you more about health than any behaviour you can watch.
The 100 gram rule is a weekly average, not a daily target. It equals about 14 grams a day, and a kitten that gains 60 grams one week and 140 the next is still on track.
The rule, and where it comes from
Newborns weigh 90 to 110 grams. They gain 10 to 15 grams a day in the first 3 weeks, roughly doubling birth weight by day 14. From week 2 to week 16 the expectation settles at 100 grams a week, a range of 70 to 130 grams being normal for a domestic shorthair. Growth then decelerates: 60 to 100 grams a week from 4 to 6 months, 30 to 60 grams a week from 6 to 9 months, and 10 to 30 grams a week from 9 to 12 months.
Two caveats keep the rule honest. Small females at 8 weeks can sit at 700 grams and be perfectly well; a male Maine Coon at the same age may weigh 1.4 kg and still be normal. And a kitten that gains 100 grams a week from a 700 gram start is gaining 14 percent of body weight weekly, while one gaining 100 grams from a 2.5 kg start is gaining 4 percent. Weight gain is judged in grams, body condition in percent.
Three checkpoints that decide everything
The nodes below are the ones worth remembering, because each answers a different question: is the start normal, is growth on pace, and is adult size plausible.
| Checkpoint | Typical weight | Weekly gain | What the number answers |
|---|---|---|---|
| 8 weeks | 800 to 1000 g | 100 g | Was the start adequate |
| 16 weeks | 1800 to 2200 g | 100 g | Is growth keeping pace |
| 6 months | 2500 to 3500 g | 60 to 100 g | Is adult size plausible |
| 9 months | 3000 to 4200 g | 30 to 60 g | Has the curve flattened |
| 12 months | 3500 to 4500 g | 10 to 30 g | Is the growth phase over |
One shortcut is worth knowing: weight at 16 weeks multiplied by 2 gives a rough adult weight. A 2.0 kg kitten at 16 weeks lands near 4.0 kg as an adult, which is a large but ordinary cat. The estimate is off by 10 to 15 percent in either direction, so treat it as a range, not a promise.
How to weigh without a fight
Use a digital kitchen scale with 1 gram resolution, not a bathroom scale, which cannot resolve a 100 gram change in a 3 kg animal. Weigh at the same time each week, before the first meal and after the litter box, and use the same surface every time. Stand on the scale holding the kitten if it will not sit still, then subtract your own weight; the error is 20 to 50 grams and repeatable, which matters more than absolute accuracy.
Write the number and the date in the same place every week, on paper or in a note on the fridge. A 4 week spreadsheet of 4 numbers beats a perfect memory of one. Weigh weekly until 6 months, every 2 weeks from 6 to 9 months, and monthly from 9 months onward. In a multi-cat house, weigh each kitten separately and mark collars, because a shared bowl hides which one is losing.
Reading the shape of the curve
Four patterns cover most of what you will see. A straight line rising 100 grams a week is normal. A line that rises then flattens for exactly 1 week, then resumes, is usually teething, vaccination or a food change, and needs no action beyond a re-weigh in 7 days. A line that flattens for 2 consecutive weeks is a problem worth a vet call. A line that falls, meaning an actual loss of 50 grams or more, is a same-day appointment.
Body condition is the other half. At 4 months you should feel ribs under light pressure, see a waist from above, and see a small belly that does not swing. A kitten at the bottom of the weight range with a body condition score of 4 out of 9 is a different patient from one at the same weight with a score of 6.
The food numbers behind the curve
A 4 month kitten at 2 kg needs about 280 to 320 kcal a day, spread over 3 to 4 meals. At 6 months, 2.8 kg and a slowing metabolism puts the need at 240 to 280 kcal a day over 3 meals. Wet food at 80 kcal per 100 gram can means 350 to 400 grams a day at 4 months, which is a lot of food and the reason many owners underfeed without noticing.
Growth is not a reason to free-feed. Free-fed kittens are the ones that arrive at 6 months at 3.8 kg with a body condition score of 7, and the extra fat cells laid down before a year are hard to lose later. Measure the daily ration, split it into 3 or 4 portions, and let the scale arbitrate.
When a flat line needs a vet
Two weeks without gain before 6 months, any weight loss, a kitten that is gaining under 50 grams a week at 12 weeks, or a sudden drop of 100 grams or more in a week all justify a visit within 48 hours. The weekly check routine and the stall checklist cover the same ground. The common causes are roundworm, coccidia, giardia, dental pain and chronic diarrhoea; less common are feline coronavirus and heart disease.
Bring the written weights to the appointment. A vet with 6 numbers can decide in 5 minutes what 20 minutes of guessing cannot, and the visit costs less than a week of supplemental feeding that fixes nothing.
A 6-week tracking plan
- Week 1: buy a 1 gram scale, weigh, and record the starting point.
- Week 2: weigh again; a gain of 70 to 130 grams is on track.
- Week 3: photograph the kitten from above beside a ruler, once a month.
- Week 4: compare the 4 numbers; a rise of 400 grams total is expected.
- Week 5: if the line is flat, book a fecal test rather than changing food.
- Week 6: adjust the daily ration by 10 percent up or down, then re-weigh in 7 days.
Kittens do not grow in a straight line, and a single odd week tells you nothing. Six weights, written down, tell you almost everything.
Frequently asked
How much should a kitten gain each week?
About 100 grams a week from 2 weeks to 4 months, which works out at 14 grams a day; 70 to 130 grams is the normal range. From 4 to 6 months expect 60 to 100 grams, and from 6 to 9 months 30 to 60 grams as growth slows toward adult size.
What if my kitten's weight is flat for a week?
One flat week is common and usually follows teething, a vaccination or a food switch, so re-weigh in 7 days. Two flat weeks in a row before 6 months, or any loss of 50 grams, is a reason to book a visit and bring a fecal sample.
Is a 16 week weight enough to predict adult size?
It gives a rough figure: weight at 16 weeks times 2 lands within 10 to 15 percent of adult weight for most domestic shorthairs. Large breeds such as Maine Coons keep growing past 2 years, so the estimate understates them and the curve should be read against breed ranges.