How to Tell How Old a Kitten Is

Last updated June 28, 2026 · 7 min read

When a kitten arrives without a birthday, you can still estimate its age closely. Three fast signs do most of the work: whether the eyes are open, which teeth have come in, and how much the kitten weighs. Used together, they get you within a week or two for any kitten under about 10 weeks old. Once you have an age, you can convert your kitten's age to human years with our calculator.

The fastest way to estimate a kitten's age

For young kittens, age signs are unusually predictable, which is why a careful estimate is often accurate within a couple of weeks. The trick is to read several signs at once rather than trusting any single one.

• Eyes: closed in a newborn, opening around day 10, fully open by 2 weeks.
• Teeth: none at birth, baby teeth starting at about 3 weeks.
• Weight: roughly 1 pound per month for the first months, so about 2 pounds at 8 weeks.

Past about 10 weeks, weight stops being a reliable guide and teeth become the better clue. For the full picture of what changes across the whole first year, see our full kitten development timeline through the first year.

Week-by-week kitten age chart

Here is what a healthy kitten tends to look like at each stage from birth to 8 weeks. Match your kitten to the closest row.

• Newborn (0 to 1 week): about 100 grams at birth, eyes closed, ears folded, cannot see or hear, no teeth. Doubles its birth weight by the end of the first week.
• 2 weeks: eyes open (around day 10) and are fully open, always blue at first. Ear canals open and hearing develops around day 14. First wobbly movements.
• 3 weeks: first baby teeth (incisors) emerge, ears point upright, the kitten starts walking and exploring, and begins investigating the litter box. Roughly 350 to 450 grams.
• 4 weeks: baby canine teeth come in. The kitten can walk, run, and begin to play, and starts retracting its claws.
• 5 weeks: premolars emerge and the kitten is ready to begin weaning onto wet food. Roughly 550 to 650 grams.
• 6 weeks: all 26 deciduous (baby) teeth are in, and weaning is well underway. Roughly 650 to 750 grams.
• 7 to 8 weeks: fully weaned and eating independently, about 2 pounds (roughly 850 to 950 grams) at 8 weeks. Reputable shelters and breeders do not place kittens younger than 8 weeks.

Estimating age by teeth

Teeth are the single most reliable age clue, especially after 6 weeks when weight gets unreliable. The eruption order is consistent enough that shelters age kittens by it.

• Baby teeth start at about 3 weeks: incisors first (2 to 4 weeks), then canines (3 to 4 weeks), then premolars (4 to 6 weeks).
• All 26 deciduous teeth are present by about 6 weeks.
• The first permanent teeth (middle incisors) appear around 12 weeks, with the second and third incisors at about 14 and 16 weeks.
• Adult teeth replace the baby teeth between 4 and 6 months, and all 30 adult teeth are in by 6 to 7 months.
• Baby teeth are smaller and sharply pointed, while adult teeth are wider with flatter edges.

Estimating age by weight

For the first five to six months, a healthy kitten's weight in pounds roughly equals its age in months. A 2-pound kitten is about 2 months old.

• A newborn weighs about 100 grams and doubles that in the first week, then gains roughly 1 pound (about 450 grams) per month for the first 6 months.
• So 2 pounds is about 2 months (8 weeks), 3 pounds about 3 months, and 4 pounds about 4 months.
• Shelter-medicine markers agree at the two-month point: a 2-pound kitten is about 8 weeks old, and a 2.5-pound kitten about 10 weeks.
• Weight reliably predicts age only through about 10 weeks. After that, growth slows and varies by kitten, so switch to teeth.

Eyes, ears, and mobility clues

Sensory and movement milestones bracket the first month tightly. Eyes and ears open on a predictable schedule, and walking is a clear 3-week marker.

• Eyes open around day 10, are fully open by 2 weeks, and are always blue at first.
• Ear canals open in the first two weeks, hearing develops by about day 14, and the ears go from folded to upright by 3 weeks.
• Walking starts around 3 weeks. A kitten walking well and playing is at least 4 weeks old.
• By the end of week 4, kittens walk, retract their claws, and begin to play.

Behavior and eye-color milestones

Behavior fills in the gaps that teeth and weight leave, and eye color marks the kitten-to-adult transition.

• The socialization window is weeks 2 to 7, the critical period for gentle handling and bonding.
• Litter-box use begins around 3 to 4 weeks, weaning onto wet food runs about 5 to 7 weeks, and independent eating arrives by about 8 weeks.
• Eye color starts shifting from blue to its adult shade around 7 weeks and settles by 8 to 12 weeks. After that, eye color no longer indicates age.
• By 6 months a kitten is about 75 percent of adult size, and it officially becomes a Junior cat at 12 months. For where that fits in the wider picture, see the six feline life stages.

When to see a vet for an age estimate

For an orphaned or stray kitten, a vet can confirm the age and start care on the right schedule. For kittens under 6 months, that estimate is usually within a couple of weeks.

• Orphaned newborns need bottle feeding with kitten milk replacer every 2 to 3 hours. Cow's milk causes severe diarrhea, and very young kittens need gentle human stimulation to eliminate.
• Vaccine and spay or neuter timing depend on an accurate age (spay or neuter is commonly done at 4 to 6 months).
• Once a kitten has grown past the predictable-aging window, the same approach used to tell how old an adult cat is takes over.

Frequently asked questions

Written by the Cats Age Calculator editorial team · How we research & fact-check