Kittens do not grow in a straight line, but they grow predictably enough that a kitchen scale tells you more about their health than almost any other home measurement. A newborn weighs 90 to 120 g. In the first two weeks it gains roughly 10 g a day, then 12 to 15 g a day through week six, and from two months onward about 100 to 125 g a week. Weigh once a week, plot the numbers, and you have a curve. A curve that bends the wrong way is usually the first sign of trouble, often days before the kitten looks sick to you.
What a normal curve looks like
Birth weight depends on litter size and the queen's condition: a single kitten may arrive at 120 g, one of five at 85 g. What matters is the direction of travel from day three, after the fluid loss of the first 24 hours has been made up. A kitten that weighs the same on day two and day four is not simply a small kitten; it is a kitten that is not getting enough milk, and that is a same-day problem.
From birth to eight weeks a healthy kitten roughly triples its birth weight, and by four months it is about ten times its birth weight. Gains are enormous early and taper steadily, which is why a 400 g month looks normal at three months and alarming at nine.
Month-by-month reference table
These are common reference ranges for an average domestic shorthair, mixed sex. Males sit 10 to 20 percent above the middle of the range from about eight weeks on, and large breeds such as the Maine Coon run well above it and keep growing long past a year.
| Age | Typical weight | Gain since previous row |
|---|---|---|
| Birth | 90-120 g | — |
| 1 week | 150-200 g | 10-15 g a day |
| 2 weeks | 200-260 g | 10 g a day |
| 3 weeks | 250-330 g | 10-12 g a day |
| 4 weeks (1 month) | 350-450 g | 100-150 g a week |
| 6 weeks | 500-650 g | 100 g a week |
| 8 weeks (2 months) | 700-900 g | 100 g a week |
| 12 weeks (3 months) | 1.1-1.5 kg | 100-125 g a week |
| 4 months | 1.5-2.0 kg | 100-110 g a week |
| 5 months | 1.9-2.5 kg | 100 g a week |
| 6 months | 2.2-3.0 kg | 75-100 g a week |
| 9 months | 3.0-4.2 kg | 40-60 g a week |
| 12 months | 3.2-4.5 kg | 0-30 g a week |
Read the table as a corridor, not a target. A kitten tracking the bottom of every row is fine if the line is parallel to the corridor; a kitten inside the range but flat for two weeks is not. The kitten weight tool does the arithmetic if you log the numbers.
Weigh the same way every time
Use a kitchen scale with 1 g resolution until the kitten passes about 2 kg, then a baby scale. Weigh at the same time of day, before a meal rather than after, and always in the same container — a plastic tub lined with a towel, tared to zero first. A kitten that has just eaten and used the litter box can swing 50 g either way, which is half a week's growth.
Once a week is enough from two months on. Under eight weeks, or any time a kitten is small for its age, weigh daily until it has posted three consecutive gains. Write the number down; the memory is a poor scale.
Read the slope, not the single number
A rough rule used in clinics is that a kitten weighs about one pound per month of age up to five months: 2 lb at eight weeks, 3 lb at twelve, 5 lb at five months. The number that matters is the gain between two weighings, compared with what the same kitten did the previous week.
Three patterns deserve a call to the vet: no gain at all across three days in a kitten under eight weeks; any weight loss under twelve weeks, where 10 percent of body weight is a serious event; and a curve that was climbing and has been flat for two weeks between two and six months, when parasites, dental pain and chronic diarrhoea usually show up first.
When a flat line is normal
Growth decelerates deliberately. Between six and nine months the weekly gain drops to 40 or 60 g, and in the last quarter of the first year many kittens gain almost nothing while still lengthening and muscling up. Owners who only read the scale conclude the food is wrong; owners who also run their hands over the ribs get the real answer — a faint rib cover, a waist behind the ribs, and no bones standing out.
Large breeds break the table entirely. A Maine Coon may take three to four years to reach adult weight and is still adding mass at eighteen months, when a domestic shorthair has been stable for a year.
What the chart cannot tell you
A scale cannot separate fat from muscle. Pair every weighing with a body condition check: ribs felt easily under a thin fat layer, a visible waist from above, a small abdominal tuck from the side. After neutering, energy needs drop by roughly 20 to 30 percent while appetite does not, which is why the curve often steepens at six months.
The chart is a trend tool, not a verdict. A kitten that is active, eating, passing normal stool and gaining on a parallel line is doing well even at the bottom of the range. One that is quiet and drifting off its own line needs a vet visit regardless of where it sits against the table.
Frequently asked
How much should a kitten weigh at 8 weeks?
Around 700-900 g at 8 weeks for most domestic kittens. Sex matters from about 6 weeks: males typically run 10-20% heavier, so compare against the range for that sex and breed, not a single number.
My kitten's weight is flat for a week. Is that an emergency?
One flat week is usually a weighing or appetite hiccup - weigh at the same time daily and recheck in 48 hours. Two flat weeks in a row, or any weight loss, needs a vet visit that same week.
Do male and female kittens grow at different rates?
Yes. Males grow faster and end up larger; the gap opens around 6 weeks and widens until roughly 10 months. Always compare with the range for the kitten's sex.