Ball pythons hatch at about 10–17 in. Adult males usually reach 3–4 ft (900–1,500 g) and females 4–5 ft (1,200–2,500 g), mostly between 2 and 5 years old. For example, a 6-month-old is usually 12–18 in (30–46 cm) and 240–480 g, and a 1-year-old female 2 ft (61 cm) and 650–800 g.
Estimates only. Every ball python grows at its own pace, mostly depending on how it is fed. See a reptile vet if your snake is losing weight, refusing food for a long time or looks unwell.
How big do ball pythons get?
Ball pythons are one of the smaller pythons. A healthy adult is usually 3 to 5 feet long (91–152 cm) and weighs roughly 900 to 2,500 grams (2–5.5 lb). Arbor View Animal Hospital's vet-written care guide gives adult males 3–4 ft and females 4–5 ft, PetMD's care sheet says 4–5 ft, and the Animal Diversity Web (University of Michigan) gives 1–1.5 m for adults. In short, ball python size is modest for a python: long enough to need a proper enclosure, small enough to handle easily.
Exceptional snakes get bigger. VetFolio's veterinary-technician guide notes wild specimens of about 6 ft, and the Animal Diversity Web cites reports of 1.83 m (6 ft) from the wild. ReptiFiles adds that larger individuals have been recorded in captivity, likely because pet snakes get more food than wild ones. A 6-foot ball python is rare, though; if a seller promises a "giant" ball python, treat it as a marketing claim.
Ball python full grown size at a glance
- Hatchling: about 10 in and 30–100 g on the keeper chart we use; VetFolio and the Animal Diversity Web give 10–17 in (25–43 cm) and 65–103 g at hatching.
- Adult male: 3–4 ft (91–122 cm), 900–1500 g (2–3.3 lb).
- Adult female: 4–5 ft (122–152 cm), 1200–2500 g (2.6–5.5 lb).
- Record length: about 6 ft (1.83 m), wild-caught (Animal Diversity Web, VetFolio).
How ball pythons compare with other pet snakes
If you are choosing between snakes, ball pythons sit in the middle. PetMD's vet-written care sheets list adult corn snakes at 4–6 ft, which is longer but much slimmer, and boa constrictors at up to 6 ft (males about 4 ft, females about 5 ft), which is longer and much heavier. A ball python's thick body means it needs bigger prey than a corn snake of the same length, but far less space and food than a boa. For the slimmer snake, see how big corn snakes get. That is a big reason ball pythons are so popular, and why the question "how long do ball pythons get?" usually has a reassuring answer.
Ball python size chart by age
This ball python size chart shows the typical total length (nose to tail tip) and weight for males and females from hatching to 5 years. Use it to check whether a young snake is on track, to plan enclosure upgrades and to compare with the calculator's result for any age in between.
| Age | Male length | Male weight | Female length | Female weight | Life stage |
|---|---|---|---|---|---|
| Hatchling | 10 in (25 cm) | 30–100 g | 10 in (25 cm) | 30–100 g | Hatchling / baby |
| 1 month | 10–12 in (25–30 cm) | 50–150 g | 10–12 in (25–30 cm) | 50–150 g | Hatchling / baby |
| 3 months | 10–12 in (25–30 cm) | 90–180 g | 10–12 in (25–30 cm) | 90–180 g | Hatchling / baby |
| 6 months | 12–18 in (30–46 cm) | 240–480 g | 12–18 in (30–46 cm) | 240–480 g | Juvenile |
| 9 months | 12–18 in (30–46 cm) | 390–750 g | 12–18 in (30–46 cm) | 390–750 g | Juvenile |
| 12 months (1 year) | 18 in – 2 ft (46–61 cm) | 500–800 g | 2 ft (61 cm) | 650–800 g | Sub-adult |
| 18 months (1.5 years) | 21 in – 2 ft 6 in (53–76 cm) | 650–950 g | 2 ft 3 in – 2 ft 6 in (69–76 cm) | 925–1,300 g | Sub-adult |
| 2 years | 2–3 ft (61–91 cm) | 800–1,100 g | 2 ft 6 in – 3 ft (76–91 cm) | 1,200–1,800 g | Adult |
| 3 years | 2 ft 6 in – 3 ft 6 in (76–107 cm) | 900–1,500 g | 3–5 ft (91–152 cm) | 1,200–2,000 g | Adult |
| 4 years | 3–4 ft (91–122 cm) | 900–1,500 g | 4–5 ft (122–152 cm) | 1,200–2,500 g | Adult |
| 5 years and older | 3–4 ft (91–122 cm) | 900–1,500 g | 4–5 ft (122–152 cm) | 1,200–2,500 g | Adult (fully grown) |
No veterinary school or zoo publishes a month-by-month growth chart for ball pythons, so this chart combines keeper sources and says where each part comes from. Months 0–9 use reptile.guide's chart, which does not split males and females; a study of 1,250 wild ball pythons (Aubret et al., 2005) found that sex differences are often undetectable in newborns. Years 1–3 use the male and female figures from MoreReptiles' keeper chart, 18 months is drawn between the 1- and 2-year rows, and the adult row uses Arbor View Animal Hospital's adult lengths with keeper-chart weights. Life stages follow Arbor View's feeding bands. Centimeters and pounds are converted and rounded.
Ball python length by age
Length is the number most people ask about, but it changes in steps rather than smoothly. On the chart, length barely moves for the first three months (10–12 in (25–30 cm) at 3 months), then sits at 12–18 in (30–46 cm) through most of the first year. By the first birthday males are 18 in – 2 ft (46–61 cm) and females 2 ft (61 cm). Between one and three years the sexes separate: males reach 2 ft 6 in – 3 ft 6 in (76–107 cm) at 3 years, while females reach 3–5 ft (91–152 cm). Because length is hard to measure on a moving snake and grows in jumps, weight is the better number to track month to month.
Ball python weight chart by age (growth chart)
This ball python growth chart plots the weight ranges from the size chart. The solid green line is the typical male weight and the dashed purple line the typical female weight; the shaded areas show the normal range for each. Use it as a ball python weight chart by age when you weigh your snake each month.
Three things stand out. First, weight climbs steadily for the first year, from about 30–100 g at hatching to 500–800 g at 12 months, while length changes in small steps. Second, the two lines split after about 9 months: at 2 years a typical male is 800–1100 g but a typical female is 1200–1800 g. Third, the lines flatten by about 4 years. A snake well above its line may simply be a big female or a fast grower, but a steep climb in an adult is more often a sign of overfeeding than of growth.
How big do male ball pythons get? Male vs female size
Male ball pythons are smaller than females, and female ball python size is the main reason ball pythons have a wide adult range. Most adult males are 3–4 ft long and weigh about 900–1,500 g; adult females are usually 4–5 ft and 1,200–2,500 g. Aubret and colleagues' 2005 study of 1,250 wild ball pythons in Togo found that adult females are larger, carry more body condition (more weight for their length) and have relatively longer jaws than males. Females also grew faster after hatching, and they reached maturity at about 95 cm snout–vent length.
| Source | Adult male | Adult female |
|---|---|---|
| Arbor View Animal Hospital (vet) | 3–4 ft (91–122 cm) | 4–5 ft (122–152 cm) |
| ReptiFiles (care reference) | 3.6–4.3 ft (109–131 cm) | 3.8–4.5 ft (114–136 cm) |
| PetMD (vet) | 4–5 ft, both sexes | 4–5 ft, both sexes |
| Keeper chart used here, 4 years + | 3–4 ft, 900–1,500 g | 4–5 ft, 1,200–2,500 g |
The size gap follows from how differently the sexes mature. VetFolio reports that males usually become sexually active at 16–18 months and about 650 g, while females mature later, at 27–31 months and at least 1,000 g. A female needs a big body to produce eggs, so she keeps growing longer. That is also why a 1,000 g snake reads very differently by sex in the calculator: as a male it is adult-sized, while as a female it is probably 14–20 months old.
Not sure of your snake's sex? Choose "Not sure" in the calculator and it uses the full range for both sexes. Arbor View notes that females tend to be larger but that the only reliable way to know is for a vet to probe the snake.
Royal python size: same snake, different name
"Royal python" and "ball python" are two names for one species, Python regius. Royal python is the usual name in the UK and Europe, and ball python in North America. Arbor View's vet guide is titled "Ball/Royal Python", and VetFolio describes the ball python as "otherwise known as the royal python". The species name regius is Latin for "royal", while "ball" comes from the snake's habit of curling into a tight ball with its head in the middle when frightened (Animal Diversity Web). So how big do royal pythons get? Exactly as big as ball pythons: about 91–152 cm (3–5 ft) as adults.
For anyone who asks "ball python, how big do they get?" in centimeters and kilograms, here is the same data as a metric royal python size chart:
| Age | Male length | Male weight | Female length | Female weight |
|---|---|---|---|---|
| Hatchling | 25 cm | 0.03–0.1 kg | 25 cm | 0.03–0.1 kg |
| 6 months | 30–46 cm | 0.24–0.48 kg | 30–46 cm | 0.24–0.48 kg |
| 1 year | 46–61 cm | 0.5–0.8 kg | 61 cm | 0.65–0.8 kg |
| 2 years | 61–91 cm | 0.8–1.1 kg | 76–91 cm | 1.2–1.8 kg |
| 3 years | 76–107 cm | 0.9–1.5 kg | 91–152 cm | 1.2–2 kg |
| Adult (4 years +) | 91–122 cm | 0.9–1.5 kg | 122–152 cm | 1.2–2.5 kg |
Royal python full size is therefore around 91–122 cm and 0.9–1.5 kg for males and 122–152 cm and 1.2–2.5 kg for females. Everything else on this page, including the enclosure and feeding advice, applies to royal pythons unchanged.
How fast do ball pythons grow and when do they stop growing?
Ball pythons grow fastest in their first year. On the chart, a typical snake goes from about 65 g at hatching to around 650 g at 12 months, roughly a tenfold gain. VetFolio says captive-raised ball pythons grow to more than 3 feet within 3 years. By 12 months a typical male has reached about 50% of its adult length and a typical female about 44%.
When do ball pythons stop growing? Most reach adult size somewhere between 2 and 5 years. Arbor View treats snakes over 2 years as adult size for feeding purposes, reptile.guide puts full size at 3–5 years, and ReptiFiles says ball pythons reach sexual maturity at 3–5 years. Males usually level off sooner than females. Like most snakes, ball pythons keep growing very slowly through adulthood, but after about 4 years the change is too small to notice from one year to the next.
What affects ball python growth rate?
- Feeding schedule: the biggest factor. Arbor View warns that many feeding guides are written for breeders who want snakes at breeding weight as fast as possible. A snake fed that way grows faster, but the vet guide also notes that obesity is a common problem in ball pythons. Our ball python feeding chart by weight follows Arbor View's slower, vet-recommended schedule.
- Sex: females grow faster after hatching and finish bigger (Aubret et al., 2005).
- Genetics and origin: reptile.guide notes that some of the largest ball pythons on record came from one region of West Africa, the Volta river area, so bloodlines matter.
- Husbandry: temperature, humidity and stress all affect appetite. VetFolio lists stress, especially from too much handling, as one of the main reasons ball pythons refuse food, and a snake that skips meals grows more slowly.
- Natural fasting: ball pythons often stop eating for weeks or months, especially in winter or the breeding season (Arbor View, VetFolio). Fasts slow growth temporarily but are usually harmless if the snake keeps its weight.
Baby and juvenile ball python size
Hatchling ball python size is about 10 inches. VetFolio and the Animal Diversity Web give a range of 10–17 in (25–43 cm), and the Animal Diversity Web lists birth weights of 65–103 g, averaging 86 g. The keeper chart we use starts a little lower, at 30–100 g, because pet-trade hatchlings vary a lot. The Animal Diversity Web notes that hatchlings are independent as soon as they hatch.
Baby ball python size through the first three months stays around 10–12 in (25–30 cm), while weight roughly doubles to 90–180 g. From about 4 months a young snake starts lengthening again; a 6-month-old is usually 12–18 in (30–46 cm) and 240–480 g.
Juvenile ball python size (6–12 months on Arbor View's bands) runs from about 12–18 in (30–46 cm) to 18 in – 2 ft (46–61 cm), with weight rising from 240–480 g to 500–800 g. A 9-month-old is usually 12–18 in (30–46 cm) and 390–750 g. During this stage Arbor View suggests feeding every 1–2 weeks, then moving to every 2–3 weeks after the first birthday. For a 1-year-old male expect 18 in – 2 ft (46–61 cm) and 500–800 g; for a female 2 ft (61 cm) and 650–800 g.
How old is my ball python? Estimating age from size
If your snake came from a rescue, a previous owner or a pet shop without records, its size is the easiest clue to its age while it is still growing. Switch the calculator to Size → age, enter its weight, length or both, and choose its sex if you know it. The tool then reads the growth chart backwards to make a ball python age by size estimate. It finds the age at which a typical snake reaches that size (the best estimate). It also finds how early a fast grower and how late a slow grower could get there (the likely range).
| Weight | Best estimate (sex unknown) | If male | If female |
|---|---|---|---|
| 100 g (3.5 oz) | about 4 weeks | under 3 months | under 3 months |
| 200 g (7.1 oz) | about 4 months | 3–5 months | 3–5 months |
| 300 g (10.6 oz) | about 5 months | 4–7 months | 4–7 months |
| 450 g (15.9 oz) | about 7 months | 6–11 months | 6–10 months |
| 600 g (1.3 lb) | about 10 months | 7–16 months | 7–11 months |
| 800 g (1.8 lb) | about 15 months | 12 months – 2 years | 12–15 months |
| 1,000 g (2.2 lb) | about 18 months | Adult-sized: age can't be told | 14–20 months |
| 1,200 g (2.6 lb) | about 22 months | Adult-sized: age can't be told | 17 months or older |
| 1,500 g (3.3 lb) | Adult-sized | Adult-sized: age can't be told | Adult-sized: age can't be told |
For example, a 300 g ball python is most likely about 5 months old (4–7 months), and a 600 g snake about 10 months (7–16 months). Length works too, but with less precision: a 24-inch snake is probably 12 months – 2 years old. If you enter both and they disagree, as with a 600 g snake that is 30 inches long, the tool says so and widens the range (7 months – 3 years). A long but light snake may be underweight, and a short, heavy one may be overweight.
The limits of a ball python age calculator
- Adults can't be aged by size. Once a snake reaches the adult range, a 3-year-old and a 25-year-old look the same. The calculator says so rather than guessing.
- Feeding history changes everything. A power-fed 1-year-old can be as heavy as a slowly raised 2-year-old.
- Measure carefully. Weigh in grams on a kitchen scale (inside a tub, minus the tub's weight). For length, photograph the snake beside a tape measure or run a piece of string along its body from nose to tail tip, then measure the string.
- Records beat estimates. Ask the seller or breeder for a hatch date. A reptile vet can also give a professional opinion during a health check.
Ball python tank size chart by age and size
The right ball python enclosure size depends on the snake's length, not its age, so this ball python tank size chart is organized by size first. ReptiFiles' guidance is the most detailed, and Arbor View Animal Hospital sets the adult minimum at 4 × 2 × 2 ft. Both agree that a snake should be able to stretch out to its full length inside the enclosure.
| Stage | Snake size | Current recommendation | Older guidance |
|---|---|---|---|
| Hatchling | Up to about 300 g | 20 × 11 × 13 in (50 × 28 × 33 cm), 10 gallons | 10–20 gal (VCA, PetMD); 10-gal floor area (VetFolio) |
| Juvenile | Under 3 ft (91 cm) | 36 × 18 × 18 in (90 × 45 × 45 cm) or larger | 20 gal for a young adult (VetFolio) |
| Adult male | About 3–4 ft (91–122 cm) | 48 × 24 × 24 in (120 × 60 × 60 cm), i.e. 4 × 2 × 2 ft | 30 gal (VetFolio); 40+ gal (PetMD) |
| Adult female | About 4–5 ft (122–152 cm) | 4 × 2 × 2 ft minimum; 5 × 2 × 2 ft for larger females (Arbor View) | 30 gal (VetFolio); 40+ gal (PetMD) |
40 gallons or 4 × 2 × 2 ft? Why the advice disagrees
If you search what size tank for a ball python, you will find answers ranging from 20 gallons to 120 gallons. The difference is mostly the age of the advice. Older guides set the minimum by the floor of a standard aquarium. VetFolio's guide gives a 10-gallon floor (20 × 10 in) for juveniles, 20 gallons for young adults and 30 gallons (36 × 12 in) for large adults. PetMD's care sheet says 10–20 gallons for juveniles and 40 gallons or more for adults, and VCA's general snake housing page says 10–20 gallons suits small or juvenile snakes. Newer welfare-based guidance asks for much more room. Arbor View's 2021 guide explains that the idea of ball pythons being stressed by space is a myth. What stresses them is exposure, meaning an enclosure without enough cover and hides. It cites research linking small enclosures with stress behaviour. A 4 × 2 × 2 ft enclosure is roughly 120 gallons by volume, about three times a 40-gallon tank.
We follow the newer guidance: a 4-ft-long adult can't stretch out in a 3-ft tank. Whatever size you choose, fill it with hides at both the warm and cool ends, plus branches, plants and ground clutter so the snake feels secure (Arbor View). For ball python tank size by age, the calculator suggests an enclosure from the typical size at the age you enter: a hatchling setup until about 300 g, a 3-ft enclosure until about 3 ft long, then the adult minimum.
How long do ball pythons live?
Ball pythons are a long commitment. Arbor View Animal Hospital and ReptiFiles both give a ball python lifespan of 15–30 years in captivity, VetFolio says 20–30 years and PetMD "up to 30 years with proper care". The Animal Diversity Web gives an average of about 20 years in captivity and about 10 years in the wild, where predators, disease and food shortages shorten lives.
The oldest ball python on record lived at the Saint Louis Zoo. CBS News reported in 2020 that the zoo's female ball python, which had lived there since 1961, was 62 years old when she laid a clutch of eggs. The zoo's herpetology manager called her "the oldest snake ever documented in a zoo". Older reference books cite smaller records, such as 47 years at the Philadelphia Zoo (VetFolio). So how long do ball pythons live? Usually two to three decades, and occasionally much longer.
A long life also means many years at adult size. A 2-year-old ball python may still have 20 or more years ahead, so plan for an adult-sized enclosure and a lifetime of rodent meals from the start.
Signs your ball python is a healthy size
Length and weight charts tell you whether a snake is on track for its age, but body shape tells you whether that weight is healthy. Our sources describe the ideal in similar ways:
- Body cross-section: Arbor View says the body should form a "soft triangle" when you look along the spine. ReptiFiles compares a healthy cross-section to a melted chocolate kiss: rounded sides with a gentle peak at the spine.
- Underweight signs: a sharply visible, ridged spine means the snake isn't eating enough (ReptiFiles).
- Overweight signs: no visible spine at all, a rounded-top body, or skin rolls when the snake bends (Arbor View, ReptiFiles).
- Weight trend: weigh monthly and record it. During a fast, Arbor View advises regular weighing to make sure the snake doesn't lose more than 10% of its body weight.
This is general information, not a diagnosis. Arbor View recommends a vet exam every 6–12 months. See a reptile vet sooner if your snake loses more than 10% of its weight or keeps getting thinner while refusing food. PetMD's care sheet also lists signs that need a vet: cloudy eyes, blisters or sores, stuck shed, discharge around the vent, lethargy, or sudden trouble moving part of the body. VetFolio stresses that a vet visit is especially important for new snakes and any snake that is losing weight.
How this ball python size calculator works
Size → age: best estimate = age where a typical snake reaches that size · range = ages where the fastest and slowest growers do
In Age → size mode the calculator converts weeks or years to months and reads the length and weight range at that age from the chart above, drawing a straight line between chart points (a 15-month-old gets a range a quarter of the way from 1 to 2 years). "Not sure" uses the widest range across both sexes. "% of adult size" compares typical length at that age with the middle of the adult range (3.5 ft for males, 4.5 ft for females). The enclosure suggestion uses ReptiFiles' size bands and Arbor View's adult minimum. The feeding interval is Arbor View's schedule for that age. For prey size, use the ball python feeding calculator.
In Size → age mode it runs the chart in reverse, as explained above. When the snake is in the adult range and the best estimate is 2 years or older, it reports "adult-sized" and does not give an exact age. Because the growth data come partly from keeper charts and growth depends heavily on feeding, treat every result as an estimate and a starting point for a conversation with your reptile vet. Keep bearded dragons too? See the bearded dragon size by age calculator. For a smaller lizard, our guide to how big leopard geckos get has a growth chart by age for males, females and giant morphs.
Frequently asked questions
How big do ball pythons get?
Most adult ball pythons are 3–5 ft (91–152 cm) long. Adult males are usually 3–4 ft (91–122 cm) and 900–1,500 g; females 4–5 ft (122–152 cm) and 1,200–2,500 g (Arbor View Animal Hospital; keeper growth charts). Rare wild snakes reach about 6 ft.
How big do male ball pythons get?
Male ball pythons usually reach 3–4 ft (91–122 cm) and 900–1,500 g (Arbor View; keeper charts). They are smaller than females and often stop growing sooner.
How big do female ball pythons get?
Females usually reach 4–5 ft (122–152 cm) and 1,200–2,500 g. Larger females may need a 5 × 2 × 2 ft enclosure (Arbor View).
How big is a 1 year old ball python?
A 1-year-old ball python is usually 18 in – 2 ft (46–61 cm) long and 500–800 g (1.1–1.8 lb). Males are typically 18 in – 2 ft (46–61 cm) and 500–800 g, females 2 ft (61 cm) and 650–800 g.
How big is a 6 month old ball python?
Usually 12–18 in (30–46 cm) long and 240–480 g (0.5–1.1 lb).
How big is a baby ball python?
Hatchlings are about 10–17 in (25–43 cm) long (VetFolio, Animal Diversity Web). On our chart a hatchling is about 30–100 g and a 3-month-old 10–12 in (25–30 cm) and 90–180 g.
When do ball pythons stop growing?
Most reach adult size between 2 and 5 years: Arbor View treats snakes over 2 years as adult size, and reptile.guide puts full size at 3–5 years. Growth after about 4 years is very slow.
How fast do ball pythons grow?
Fastest in the first year, when weight rises from under 100 g to about 650 g on our chart. VetFolio says captive-raised ball pythons pass 3 ft within 3 years.
How big do royal pythons get?
Royal pythons are the same species as ball pythons (Python regius), so they reach the same size: about 91–122 cm for males and 122–152 cm for females.
What size tank does a ball python need?
ReptiFiles suggests about 20 × 11 × 13 in (a 10-gallon tub) for hatchlings up to 300 g, 36 × 18 × 18 in for juveniles under 3 ft, and at least 48 × 24 × 24 in (4 × 2 × 2 ft) for adults. Arbor View says larger females need 5 × 2 × 2 ft.
Is a 40 gallon tank big enough for a ball python?
Only for a young snake. PetMD's care sheet lists 40+ gallons for adults, but newer guidance from ReptiFiles and Arbor View Animal Hospital asks for at least 4 × 2 × 2 ft, about three times the volume of a 40-gallon tank, so an adult can stretch out fully.
How can I tell how old my ball python is?
While it is growing, weight is the best clue: a 300 g ball python is probably 4–7 months old and a 600 g snake 7–16 months. Once it reaches adult size, its exact age can't be estimated from size; seller or breeder records are the only reliable source.
How long do ball pythons live?
Usually 15–30 years in captivity (Arbor View, ReptiFiles) and about 10 years in the wild (Animal Diversity Web). A Saint Louis Zoo ball python was 62 years old in 2020 (CBS News).
How long do ball pythons get?
Most adults are 3–5 ft long; the longest reliable records are around 6 ft (1.83 m), from wild snakes (Animal Diversity Web, VetFolio).
This calculator gives an estimate for education and fun. Every pet ages differently — for health decisions, talk to your veterinarian.