Axolotls hatch at about 11 mm and reach adult size, usually 9–10 in (23–25 cm), at around 12–18 months, though they keep growing slowly for life. For example, a 3-month-old is usually 1.6–4.3 in (4.1–10.8 cm) and a 6-month-old 3.4–7.9 in (8.7–20 cm) on our chart.
Estimates only. Axolotls grow at very different speeds depending on water temperature, food and space. Weights on this page are calculated from length. See an amphibian vet if your axolotl stops eating, loses weight or floats.
How big do axolotls get?
Most adult axolotls are 9–10 inches (23–25 cm) long from snout to tail tip. That's the figure given by both VCA Animal Hospitals and LafeberVet's veterinary information sheet. Big individuals reach 12 inches (30 cm): the Animal Diversity Web says axolotls average 20 cm (8 in) but can grow to more than 30 cm, and PetMD says they "can top out at 30 cm". Axolotl length is always measured from the snout to the tip of the tail. So if you are asking "axolotl how big do they get?", picture something about the length of a school ruler's 25 cm mark: much bigger than a goldfish, much smaller than a cat.
Adult axolotl size also varies by source and by care. Caudata.org, a long-running salamander-keeping reference, gives a typical adult length of 20–28 cm (8–11 in). The San Diego Zoo describes a wide 15–45 cm range, with most about 9 inches. Weight follows length: the Animal Diversity Web gives 60–110 g for adults, the San Diego Zoo 2–8 oz (56–226 g), and the Ambystoma Genetic Stock Center says adults can weigh as much as 300 g.
Axolotl full grown size at a glance
- Hatchling: about 11 mm (under half an inch).
- 6 months: 3.4–7.9 in (8.7–20 cm), about 60% of adult length.
- 12 months: 7.1–9.8 in (18–25 cm), sexually mature.
- Average axolotl size as an adult: 7.9–11 in (20–28 cm) and roughly 60–165 g on our chart; 9–10 in (23–25 cm) for most (VCA).
- Biggest reported: over 43 cm (17 in) according to Caudata.org; 45 cm (18 in) at the top of the San Diego Zoo's range.
Axolotl growth chart (size by age)
This axolotl growth chart shows typical total length and weight from hatching to adulthood. Use this axolotl size by age table as an axolotl size chart to check whether a young axolotl is on track, or as an axolotl age size chart when you know the hatch date. The calculator gives the same numbers for any age in between.
| Age (after hatching) | Length | Weight | Growth stage |
|---|---|---|---|
| Hatching | 0.4–0.5 in (1–1.3 cm) | <0.1 g (<0.1 oz) | Hatchling |
| 1 month | 0.7–1.9 in (1.8–4.7 cm) | <0.1–0.8 g (<0.1 oz) | Larva (back legs) |
| 2 months | 1–3.1 in (2.5–7.8 cm) | 0.1–3.5 g (<0.1–0.1 oz) | Juvenile |
| 3 months | 1.6–4.3 in (4.1–10.8 cm) | 0.5–9.5 g (<0.1–0.3 oz) | Juvenile |
| 4 months | 2.2–5.5 in (5.6–13.9 cm) | 1.3–20 g (<0.1–0.7 oz) | Juvenile |
| 6 months | 3.4–7.9 in (8.7–20 cm) | 4.9–60 g (0.2–2.1 oz) | Sub-adult |
| 9 months | 5.3–8.9 in (13–23 cm) | 18–85 g (0.6–3 oz) | Sub-adult |
| 12 months (1 year) | 7.1–9.8 in (18–25 cm) | 44–117 g (1.5–4.1 oz) | Adult |
| 18 months (1.5 years) | 7.5–10.4 in (19–27 cm) | 51–140 g (1.8–4.9 oz) | Adult |
| Adult (2 years +) | 7.9–11 in (20–28 cm) | 60–165 g (2.1–5.8 oz) | Adult (grows slowly for life) |
No veterinary school publishes a month-by-month axolotl chart, so this one joins sourced anchor points with straight lines and says where each comes from. Slow growers: about 1 cm at hatching (axolotl.org), "about an inch" at 1.5–2 months in the Ambystoma Genetic Stock Center's cool laboratory colony, about 18 cm at 12 months (LafeberVet's size at sexual maturity) and 20 cm as adults (Animal Diversity Web average). Fast growers: 1.3 cm at hatching and 3.2 cm two weeks later in warm water with daily live food (axolotl.org, a hobby reference), about 20 cm by 6 months (Caudata.org notes maturity at about 20 cm can come from 6 months), 25 cm at 12 months (VCA and LafeberVet's typical adult) and 28 cm as adults (Caudata.org). Weights are calculated from length (see below).
The axolotl growth chart below plots the length column. The line is the typical length and the shaded band runs from slow to fast growers.
The curve shows the classic shape: slow for the first few weeks while larvae grow their legs, very steep from about 1 to 9 months, then flattening once the axolotl matures at about a year. After 2 years the chart stays flat, but axolotls never stop growing completely. Researchers describe the axolotl as "an indefinitely growing animal" that keeps increasing in size throughout life (Vieira et al. 2020).
Axolotl weight chart: how much does an axolotl weigh?
So how much does an axolotl weigh? An adult usually weighs 60–110 g (2–4 oz) according to the Animal Diversity Web, and up to 226 g (8 oz) according to the San Diego Zoo. Exceptional animals reach 300 g (Ambystoma Genetic Stock Center).
No source we found publishes axolotl weight by age, so the axolotl weight chart below is calculated rather than measured. We assume weight rises with the cube of length (an animal twice as long is about eight times as heavy) and calibrate it so that a 20 cm axolotl weighs 60 g, matching the Animal Diversity Web's average adult length and lower adult weight. The result agrees well with the sources: a 25 cm axolotl comes out at about 117 g and a 30 cm one at about 203 g, inside the San Diego Zoo's range.
| Age | Weight | Ounces | Typical (middle) value |
|---|---|---|---|
| 2 months | 0.1–3.5 g | <0.1–0.1 oz | 1 g at 5.1 cm |
| 3 months | 0.5–9.5 g | <0.1–0.3 oz | 3.1 g at 7.4 cm |
| 4 months | 1.3–20 g | <0.1–0.7 oz | 6.9 g at 9.7 cm |
| 6 months | 4.9–60 g | 0.2–2.1 oz | 22.2 g at 14.4 cm |
| 9 months | 18–85 g | 0.6–3 oz | 43.2 g at 17.9 cm |
| 12 months (1 year) | 44–117 g | 1.5–4.1 oz | 74.5 g at 21.5 cm |
| 18 months (1.5 years) | 51–140 g | 1.8–4.9 oz | 88.3 g at 22.8 cm |
| 24 months (2 years) | 60–165 g | 2.1–5.8 oz | 103.7 g at 24 cm |
Weigh an axolotl in a small container of its own tank water on a kitchen scale, subtracting the container and water. A single reading matters less than the trend: a young axolotl should keep gaining, and an adult should hold steady. Because axolotls hold different amounts of water and food at different times, compare readings taken at the same time of day, before feeding.
How big can an axolotl get? Biggest axolotls
How big can an axolotl get? The sources agree that anything over 30 cm (12 in) is unusual. Wikipedia sums up the literature as "any greater than 30 cm (12 in) is rare". The biggest axolotl sizes we found in credible sources are:
- Over 43 cm (17 in): Caudata.org notes specimens over 43 cm total length are known (hobby reference).
- 45 cm (18 in): the upper end of the San Diego Zoo's 15–45 cm range, and Beardsley Zoo's "up to 18 inches".
- Up to 300 g: the heaviest weight given by the Ambystoma Genetic Stock Center.
We found no Guinness World Records entry for the largest axolotl, and no measured, dated record animal, so we don't name one. Very large axolotls are usually old ones, because growth never fully stops. The calculator treats lengths over 46 cm or weights over 300 g as probable measuring mistakes.
Baby and juvenile axolotl size
Baby axolotl size at hatching is tiny: most larvae are about 11 mm, or 10–13 mm, less than half an inch (axolotl.org). In warm water with daily live food, axolotl.org measured about 14 mm at 4 days, 20 mm at 9 days and 32 mm at 14 days. Front legs appear at about 20 mm and back legs from about the third week. In the Ambystoma Genetic Stock Center's cooler colony, larvae reach "about an inch" only at 1.5–2 months. That gap is a good illustration of how much temperature and food matter.
Juvenile axolotl size starts at about 5 cm (2 in). The Ambystoma Genetic Stock Center describes rapid growth "at juvenile stages (5cm-adult size in 6 months)". On our chart a 3-month-old is usually 1.6–4.3 in (4.1–10.8 cm) and a 6-month-old 3.4–7.9 in (8.7–20 cm). The Stock Center switches young axolotls from live brine shrimp to small pellets at about 4 cm and to larger pellets at about 15 cm (6 in), which makes length a practical guide to feeding as well as age.
For what happens to the body at each of these ages — gills, legs and toes — see our interactive axolotl life cycle explorer.
How fast do axolotls grow and when do they stop growing?
How fast do axolotls grow? Fastest between about 1 and 9 months. On the chart, length goes from about 1 cm at hatching to 3.4–7.9 in at 6 months and 7.1–9.8 in at 12 months. Caudata.org notes that well-fed axolotls at good temperatures can reach 25 cm and sexual maturity in under 6 months, while cooler, slower-fed animals take more than a year.
When do axolotls stop growing? Most of the growth is finished by about 12–18 months, when axolotls reach maturity; the AnAge database puts maturity at 548 days (18 months). After that growth slows to a crawl but doesn't stop: the 2020 Gerontology review describes axolotls continuing to grow after sexual maturity, with a 3-year-old visibly bigger than a 1-year-old. That slow lifelong growth is why the chart's adult row is a range rather than a single number.
What affects axolotl growth rate?
- Temperature: warmer water speeds growth and development; colder water slows it (Ambystoma Genetic Stock Center). But warm is not better for health: the Stock Center keeps axolotls at 15–18 °C and never above about 22 °C, and VCA warns of infections above 24 °C.
- Diet: the Stock Center says larval growth depends on "frequency and amount of food". Young axolotls should be offered food daily (VCA).
- Stocking density: crowding slows growth and causes injuries. The Stock Center starts with no more than 50–100 eggs per bowl and reduces numbers progressively as larvae grow.
- Tank size and water quality: a cramped, dirty tank means more waste and stress. LafeberVet says ammonia and nitrite should be 0 ppm.
- Injuries and regeneration: axolotls regrow lost legs and tail tips (VCA), but regrowth takes energy and months, and a regrowing tail makes an axolotl measure short.
How old is my axolotl? Estimating age from size
If your axolotl came from a pet shop or a previous owner without records, size is the best clue to its age while it is still growing. Switch the calculator to Size → age and enter its length, weight or both. The tool reads the growth chart backwards: the best estimate is the age when a typical axolotl reaches that size, and the range runs from how early a fast grower and how late a slow grower would get there. This axolotl age by size table shows the results for common lengths:
| Length | Best estimate | Likely range |
|---|---|---|
| 1 in (2.5 cm) | about 3 weeks | 1 week – 2 months |
| 2 in (5.1 cm) | about 9 weeks | 5 weeks – 4 months |
| 3 in (7.6 cm) | about 3 months | 8 weeks – 5 months |
| 4 in (10.2 cm) | about 4 months | 3–7 months |
| 5 in (12.7 cm) | about 5 months | 4–9 months |
| 6 in (15.2 cm) | about 7 months | 4–10 months |
| 7 in (17.8 cm) | about 9 months | 5–12 months |
| 8 in (20.3 cm) | about 11 months | 6 months or older |
| 9 in (22.9 cm) | Adult-sized | Adult-sized: exact age can't be told |
| 10 in (25.4 cm) | Adult-sized | Adult-sized: exact age can't be told |
For example, a 3-inch axolotl is most likely about 3 months old (8 weeks – 5 months), a 6-inch one about 7 months (4–10 months), and an 8-inch one about 11 months old. A 10-inch axolotl is adult-sized, so its exact age can no longer be estimated. Weight alone gives a rougher answer because our weights are calculated: a 20 g axolotl reads as about 6 months (4–9 months). If length and weight disagree, as with a 15 cm axolotl weighing 80 g, the tool says so and widens the range.
How to tell how old an axolotl is: the limits
- Adults can't be aged by size. Once an axolotl reaches adult size, a 2-year-old and a 10-year-old can look almost the same. The calculator says so rather than guessing.
- Temperature changes everything. The same 3-month-old can be 4 cm in a cool lab tank or 10 cm in a warm, well-fed one.
- Sexing gives a minimum age. Axolotls can't be sexed until they are mature at about a year (Ambystoma Genetic Stock Center). LafeberVet notes that mature males develop a cloacal bulge, so a clearly male axolotl is probably at least 10 months old.
- Records beat estimates. Ask the breeder for a hatch date. An amphibian vet can give a professional opinion during a check-up.
Axolotl tank size by size and age
What size tank for an axolotl? The current vet guidance is at least 20 gallons (78 L) for one adult. LafeberVet sets 78 L (20 gallons) as the minimum for adults and says a young axolotl can be housed in 38 L (10 gallons). Tree of Life Exotic Pet Medical Center specifies a 20-gallon long tank for one axolotl and adds at least 10 gallons for each additional one. This axolotl tank size by age table follows that guidance, organised by length because size, not age, decides how much room an axolotl needs:
| Stage | Minimum tank | Notes and sources |
|---|---|---|
| Larvae (under 5 cm / 2 in) | Shallow bowls or a small tank | The Ambystoma Genetic Stock Center raises larvae in shallow bowls about 20 cm (8 in) across, no more than 50–100 per bowl, thinning them out as they grow; LafeberVet says a young axolotl can live in a 10-gallon (38 L) tank. |
| Juveniles (5–18 cm / 2–7 in) | At least 10 gallons (38 L), about 20 × 10 × 12 in | LafeberVet: a young axolotl can be housed in a 38 L (10 gallon) aquarium. Plan the upgrade early, because many juveniles reach adult size within months. |
| Adults (18 cm / 7 in and up) | At least 20 gallons (78 L), about 30 × 12 × 12 in | LafeberVet and Tree of Life Exotics: at least 20 gallons (78 L) for one adult — a 20-gallon long is about 30 × 12 × 12 in (76 × 30 × 30 cm) — plus about 10 gallons for each extra axolotl (Tree of Life). Older guidance allows 10 gallons (PetMD). |
10 gallons or 20? Why the advice disagrees
You will find axolotl tank size advice from one gallon to 40 or more. Older guidance is smaller: PetMD's care page recommends starting "with one Axolotl in a 10-gallon tank" and allows up to three per 10 gallons, and the Ambystoma Genetic Stock Center houses two adults in a ten-gallon aquarium (laboratories also keep adults in one-gallon bowls with frequent water changes). Caudata.org calls a 60 × 30 × 37 cm (24 × 12 × 15 in) aquarium adequate for two adults.
The bigger modern minimums are about stability, not swimming space. A larger volume of water heats up more slowly in summer and dilutes waste, and both temperature and waste are leading causes of illness. Floor space matters more than height for this bottom-dwelling animal, which is why vets specify a "long" tank. Our calculator suggests the current minimum for the size it predicts.
Signs your axolotl is underweight, overweight or stunted
A chart tells you whether an axolotl is the expected size for its age; body condition tells you whether that size is healthy. This is general information, not a diagnosis.
- Underweight: steady weight loss on your monthly weigh-ins, or an axolotl that refuses food, points to a problem. VCA lists anorexia (not eating) among the most common problems in pet axolotls and links many of them to poor water quality.
- Overweight: VCA also lists obesity as a common problem. An adult that keeps gaining weight after growth has slowed, while being fed every day, is probably overfed. VCA advises feeding adults every 2–3 days, only as much as they eat in 2–5 minutes.
- Stunted growth: a young axolotl that stays small for weeks is often in water that is too cold, too crowded or too dirty, or isn't getting enough food. Check the stocking density and the water before anything else (Ambystoma Genetic Stock Center).
- Floating and swelling: VCA notes that water above 24 °C can make axolotls float uncontrollably; swelling or floating that doesn't settle needs a vet.
See an exotic or amphibian vet if your axolotl stops eating, loses weight, floats, or has skin patches or bulging eyes (VCA links bulging eyes to excess nitrite). Bring a water test result with you, because most axolotl illnesses start in the tank.
Axolotl size compared with other pet amphibians and reptiles
How does an axolotl measure up against other pets? It is big for an amphibian — longer than most pet frogs and similar to its relative the tiger salamander — but small next to the reptiles on PetYearsCalc:
| Animal | Adult length | Adult weight | Source |
|---|---|---|---|
| Axolotl | 9–10 in (23–25 cm) typical; up to 12 in+ | 60–110 g (ADW); up to 226 g (San Diego Zoo) | VCA, LafeberVet, Animal Diversity Web |
| Eastern tiger salamander | 7–13 in (17–33 cm) | — | Animal Diversity Web; the axolotl's metamorphosing relative |
| African clawed frog | 2–5 in (5–12 cm) | — | Animal Diversity Web; males 5–6 cm, females 10–12 cm |
| Leopard gecko | 7–10 in | 45–90 g | Arbor View, LafeberVet |
| Bearded dragon | 15–26 in | 300–550 g | See our bearded dragon size chart |
| Ball python | 3–5 ft (91–152 cm) | 900–2,500 g | See our ball python size chart |
How this axolotl size calculator works
Weight = 7.5 × (length in cm)³ ÷ 1000 grams · Size → age: best estimate = age when a typical axolotl reaches that length
In Age → size mode the calculator converts weeks or years to months after hatching and reads the length range from the growth chart, drawing straight lines between the sourced anchor points. Weight is calculated from length with the formula above, so treat it as a guide. "% of adult size" compares the typical length at that age with the middle of the adult range (24 cm). The growth-stage label uses the same stages as our life cycle explorer, and the tank suggestion follows LafeberVet's and Tree of Life Exotics' minimums.
In Size → age mode it runs the chart in reverse. A weight is first turned into the matching length. When the axolotl is in the adult range and the best estimate is 12 months or more, the tool reports "adult-sized" and does not give an exact age. Because growth depends so much on temperature, food and crowding, treat every result as an estimate. To find out what your axolotl's age means in human years, or how long axolotls live, see the axolotl lifespan and age calculator.
Frequently asked questions
How big do axolotls get?
Most adults are 9–10 in (23–25 cm) long (VCA, LafeberVet), and some reach 12 in (30 cm) or more. Adults usually weigh 60–110 g (Animal Diversity Web). On our chart a typical adult is 7.9–11 in (20–28 cm).
How big is a 6 month old axolotl?
Usually 3.4–7.9 in (8.7–20 cm) long and about 4.9–60 g (calculated), roughly 60% of adult length. Warm, well-fed axolotls are at the top of the range.
How big is a 3 month old axolotl?
Usually 1.6–4.3 in (4.1–10.8 cm). Growth is fastest between about 1 and 9 months.
How big is a baby axolotl?
About 11 mm (10–13 mm, under half an inch) at hatching (axolotl.org). Larvae reach about an inch at 1.5–2 months in a cool laboratory colony (Ambystoma Genetic Stock Center), and much sooner in warm water with daily live food.
How big is a 1 year old axolotl?
Usually 7.1–9.8 in (18–25 cm), about 90% of adult length. Axolotls are sexually mature at about one year (Ambystoma Genetic Stock Center), at roughly 18 cm (LafeberVet).
When do axolotls stop growing?
Most growth is over by 12–18 months, but axolotls never stop growing completely: researchers describe them as indefinitely growing animals that keep getting bigger throughout life (Vieira et al. 2020).
How fast do axolotls grow?
Fastest between about 1 and 9 months. Speed depends on temperature, food and crowding: the Ambystoma Genetic Stock Center says juveniles go from about 5 cm to adult size in roughly 6 months, and Caudata.org notes some reach 25 cm in under 6 months.
How much does an axolotl weigh?
Adults usually weigh 60–110 g, 2–4 oz (Animal Diversity Web), and up to 226 g, 8 oz (San Diego Zoo). The heaviest reach about 300 g (Ambystoma Genetic Stock Center).
How can I tell how old my axolotl is?
While it is growing, measure its length: a 3-inch axolotl is probably 8 weeks – 5 months old and a 6-inch one 4–10 months. Once an axolotl reaches adult size, its exact age can't be estimated from size; breeder records are the only reliable source.
How big can an axolotl get?
Anything over 30 cm (12 in) is rare. Caudata.org notes specimens over 43 cm (17 in), and the San Diego Zoo's range goes up to 45 cm (18 in). We found no Guinness record for the biggest axolotl.
What size tank does an axolotl need?
At least 20 gallons (78 L) for one adult (LafeberVet), ideally a 20-gallon long, plus about 10 gallons per extra axolotl (Tree of Life Exotics). A young axolotl can start in 10 gallons (38 L). Older guides, including PetMD, allow 10 gallons for one adult.
Is my axolotl too small for its age?
Not necessarily. Axolotls kept cool grow much more slowly than warm ones, so a slow grower can be healthy. If a young axolotl stays the same size for weeks, check water temperature, quality, crowding and feeding, and see an amphibian vet if it stops eating.
How long is an axolotl in inches?
Most adults are 9–10 inches (23–25 cm) long; hatchlings are under half an inch, 6-month-olds usually 3.5–8 inches, and 1-year-olds 7–10 inches on our chart.
This calculator gives an estimate for education and fun. Every pet ages differently — for health decisions, talk to your veterinarian.