Kitten Weight Calculator
Is your kitten growing on track?
A wide band from two published sentences, not a verdict. Your vet knows your pet.
How to use the kitten weight calculator
- Enter weight now. Grams are shown as well as the unit you typed, because the band is built in grams.
- Enter age in weeks. The band runs from birth through 16 weeks. After that it stops.
- Pick queen or tom. That switches Merck's average adult weight. It does not move the kitten band.
- Read the place line. Inside the wide band is not a prize. Outside it is not a diagnosis.
- Use the gram columns if you are tracking an orphan on a gram scale. Pounds hide a stall that grams still show.
The band is arithmetic, not a clinic chart
Merck's feeding chapter gives two figures this page is allowed to add. Normal birth weight is 90–100 g. For the first 3–4 months, kittens gain 50–100 g a week. The low edge of a week is 90 g plus 50 g times the weeks. The high edge is 100 g plus 100 g times the weeks.
At 8 that is 490 g to 900 g. The opening weight is 862 g, and the place line says Inside the wide band. Being inside that span means the arithmetic contains you. It does not mean the kitten has been examined.
No other site's week-by-week poster was copied. If you have seen a tighter chart, it came from somewhere else. This page would rather be wide and cited than narrow and borrowed.
When the rapid gain is supposed to ease off
Merck says the growth rate starts to plateau around 150–160 days and is usually finished by 200–220 days. Sixteen weeks is inside the 'first 3–4 months' window, so the table stops there. A 5-month-old is past the sentence this band is built from. The page will say so instead of extending the straight line.
Adult size on the screen is an average, not a forecast. Queens average 6.2 lb in Merck's mature ideal (2.8 kg). Toms average 3.2 kg. Switching sex moves that line and leaves the kitten band where it was. A single kitten can finish above or below the average. The average is a landmark, not a target to diet toward.
Kittens generally move to an adult diet between 8 and 12 months. That countdown is on the feeding page, because it changes food, not the scale.
What to do with one reading
One weight inside the band is a snapshot. The useful pattern is several weights a few days apart, especially under 8 weeks, where a stall matters more than a single gram total. Merck's weekly gain is an average pace, so a kitten can have a slow day and a faster day and still fit the week.
Orphan kittens and bottle volumes are not on this page. If you are feeding with a syringe, the rescue or the clinic has a volume chart. Do not convert this band into a milk dose.
If the place line says outside the band, weigh again on the same scale before you change anything. Scales disagree. A true stall, or a true drop, is a call. The sentence on the result is a comparison with two published ranges, not a grade.
Wide band from birth through 16 weeks
| Age | Band low | Band high |
|---|---|---|
| Birth | 90 g | 100 g |
| 2 weeks | 190 g | 300 g |
| 4 weeks | 290 g | 500 g |
| 8 weeks | 490 g | 900 g |
| 12 weeks | 690 g | 1300 g |
| 16 weeks | 890 g | 1700 g |
Built from Merck: birth weight 90–100 g, plus 50–100 g each week. The rapid-gain sentence covers the first 3–4 months, so the table stops at 16 weeks. Not a pass or fail.
Tips and common mistakes
- Record grams. A tenth of a pound is several days of the low weekly gain.
- Do not treat the high edge as a goal. The high edge is 100 g of gain every week plus a 100 g birth, which is the top of a range, not a score to beat.
- Sex changes only the adult average. It will not 'fix' a kitten who is outside the band.
When to call your vet
- The kitten loses weight, or fails to gain, especially before 8 weeks.
- The place line is outside the band on two weigh-ins with the same scale.
- The kitten is older than 16 weeks and you wanted this band to keep going. Ask the clinic for a check instead of stretching the line.
- You are raising an orphan and you need a feeding volume.
Frequently asked questions
How much should a kitten weigh at 8 weeks?
On this page the 8-week band is 490 g to 900 g, built as birth weight plus eight weeks of Merck's 50–100 g gain. The opening kitten at 862 g is Inside the wide band.
How fast do kittens grow?
Merck: 50–100 g a week for the first 3–4 months, then a plateau around 150–160 days, with growth usually finished by 200–220 days. This page stops the straight band at 16 weeks.
When is a kitten fully grown?
Usually by about 200–220 days, according to the same chapter. Adult diet timing is later in wording: sometime between 8 and 12 months. The adult weights shown are averages, 2.8 kg for queens and 3.2 kg for toms.
Is my kitten on track?
The place line only says whether today's grams sit inside a wide band. Inside the wide band is not a health grade. Two weights a few days apart tell you more than one reading.
Why is the band so wide?
Because Merck published a birth range and a weekly range, not a single target for each week. Adding the low to the low and the high to the high keeps every cited number and refuses a fake midpoint.