Guinea Pig Years to Human Years Calculator and Lifespan

A 1-year-old guinea pig is about 24 in human years, a 2-year-old is 35, a 4-year-old is 57 and a 6-year-old is 79. Guinea pigs grow up fast: a pup is weaned at 3 weeks (human 3), can breed at 2 months (human 12) and reaches adult weight by its first birthday. After that each guinea pig year adds 11 human years until age 6, the typical lifespan of a well-kept pet.

Enter your guinea pig’s age in weeks, months or years, or its birth date, and the guinea pig years calculator returns the human-equivalent age, the life stage and the age your guinea pig becomes a senior. It also converts human years to guinea pig years and shows how the result compares with the popular online chart and the times-12 rule. Below the calculator, this page answers how long guinea pigs live, how to tell a guinea pig’s age and what changes from breed to breed.

How to use the guinea pig years calculator

Pick a breed or coat type, enter an age and read the human equivalent.

1. Pick a breed, or “Not sure”. If you do not know the breed, choose the coat type: short-haired, rosetted (Abyssinian type), long-haired, curly, hairless or mixed. Coat type and breed do not change the result, because no study has found a breed difference in lifespan. The choice sets the care notes that come with the result.
2. Enter the age. Use weeks for a pup under 12 weeks, months for a young guinea pig and years for an adult. Decimals work, and a birth date works too. The first months matter most: a guinea pig gains 12 human years between birth and 2 months of age.
3. Read the result. You get the human age, the life stage and the age at which your guinea pig becomes a senior (4 years, human 57).
4. Switch to human to guinea pig years to turn a person’s age into a guinea pig age. A 12-year-old child matches a 2-month-old guinea pig, and an 18-year-old matches a 6-month-old.

A guinea pig older than 6 is labelled “past the typical lifespan for a pet guinea pig”. That describes where it sits on the scale and is not a prognosis. The scale stops at 122 human years, the oldest verified human age, which a guinea pig reaches at 14 years 10.5 months, the age of the oldest guinea pig on record.

The calculator is for pet guinea pigs (Cavia porcellus). It does not apply to wild cavies such as Cavia aperea, which live about 3 years in the wild, or to cuy, the larger Andean meat lines that can weigh 2 to 3 kg.

Guinea pig years to human years chart

A 3-week-old guinea pig is 3 in human years, a 2-month-old is 12, a 6-month-old is 18, a 1-year-old is 24 and a 5-year-old is 68. The chart shows this calculator next to the popular online chart (Omni Calculator, the top Bing result for “guinea pig years to human years”) and the simple times-12 rule.

A guinea pig at the UK median age at death, 4.03 years, reads 57.3 here.

Why the popular chart breaks after age 4

The popular chart makes a 1-month-old guinea pig 14, a 1-year-old 50 and a 2-year-old 68, then adds 24 human years for every guinea pig year. At that pace a 4.25-year-old guinea pig passes 122, the oldest age any human has reached. A 5-year-old reads 140 and an 8-year-old 212. A typical pet guinea pig lives 5 to 8 years, so the chart puts most healthy guinea pigs past the human record. Omni calls its result a rough estimate, and the same table is copied on other calculator sites.

Times 12 has the opposite problem. It makes a 2-month-old guinea pig 2 in human years, at the age when sows and boars can already breed, and a 6-month-old 6, when the guinea pig is nearly full size. It comes close to this calculator only around age 7 (84 against 83.8).

This calculator ties the first year to measured milestones (weaning, sexual maturity, adult size, adult weight) and then sets the pace so a 6-year-old reads 79, US life expectancy at birth. The method section lists the anchors and sources.

Human years to guinea pig years

A 12-year-old person matches a 2-month-old guinea pig, a 24-year-old matches a 1-year-old and a 79-year-old matches a 6-year-old.

How long do guinea pigs live?

Pet guinea pigs in UK veterinary care die at a median age of about 4 years, and well-kept pets commonly live 5 to 8 years. The oldest on record, Snowball, lived 14 years 10.5 months.

The 4-year figure comes from the only large study of pet guinea pig deaths. VetCompass, a research programme at the Royal Veterinary College, analysed the records of 51,622 guinea pigs seen at 1,003 UK vet practices in 2019. Among the 674 deaths with a known age, the median age at death was 4.03 years, half died between 2.56 and 5.44 years, and the oldest was 10 (O’Neill et al. 2024, PLOS ONE). The authors note that this is slightly below the 5 to 7 years usually reported.

A survival analysis of the same deaths (Mata 2025, PeerJ) built a life table for British pet guinea pigs:

The risk of death per half-year was highest from age 4 on. A UK owner survey cited by Mata found a mean lifespan of 4.1 years across 3,390 guinea pigs, with some reaching 13 and 5.2% living past 9.

Vets and animal charities quote longer figures:

• MSD Veterinary Manual: 5 to 8 years (MSD, guinea pig description).
• RSPCA: “typically guinea pigs live for 5-6 years, but some may live longer” (RSPCA).
• VCA Animal Hospitals: an average of 5 to 6 years, with some reaching 8 to 10 (VCA).
• Blue Cross and Guinness World Records: 4 to 8 years (Blue Cross).

The two kinds of figure measure different things. A median age at death counts every guinea pig that died under vet care, including young animals lost to illness, and 74% of those deaths were euthanasia. A care-guide lifespan describes what a healthy, well-kept pet can expect. This calculator uses 6 years as the typical lifespan, the middle of the vet and charity ranges.

Do male or female guinea pigs live longer?

The evidence is mixed. In the VetCompass data the median age at death was 4.58 years for females and 3.74 for males (O’Neill et al. 2024). Mata’s survival analysis of the same 674 deaths found no significant difference between the sexes, and none for neutering either. The survival test is the stronger of the two, so the calculator uses one scale for both sexes.

Guinea pig life stages

A guinea pig is a pup until 3 weeks, a juvenile until 6 months, a young adult until 1 year and an adult until 4. It is a senior from 4 years (human 57) and geriatric from 5 (human 68).

Sources for the stages: MSD Veterinary Manual (physiological data), Trillmich et al. 2006 (Journal of Zoology 268:285-294) for female puberty from about 40 days, Witkowska et al. 2014 for adult weight and bone growth, PetMD for adulthood at 6 months and the senior stage at 4, and O’Neill et al. 2024 for adult weight and disorder ages.

When is a guinea pig full grown?

A guinea pig reaches about full size at 6 months and its adult weight at 8 to 12 months. A CT study of guinea pig bones found that the skeleton keeps developing after the first year, when most guinea pigs have reached full weight (Witkowska et al. 2014). The median adult weight in UK vet records is 1.05 kg, 1.10 kg for males and 1.00 kg for females.

Many care guides say a sow must have her first litter before 6 months or her pelvis will fuse. A 2024 CT study of 23 sows found no fusion of the pubic symphysis before 12 months in bred or unbred sows (Vieu et al. 2024). Breeding pet guinea pigs is still not advised: difficult births are common and caesarean sections have a poor survival rate for the mother (MSD).

When is a guinea pig a senior?

A guinea pig is a senior from about 4 years old, which is 57 in human years. PetMD puts the senior stage at 4, and UK vet guides give 4 to 5. No veterinary body defines a fixed age. The MSD manual notes that hyperthyroidism is typically seen in guinea pigs over 3 and tumours in “middle-aged (3 years old) or older” animals, so health checks matter before the senior label applies. The calculator calls a guinea pig geriatric from 5 (human 68), the age at which life-cycle guides call it old.

The guinea pig in the photo is a mature adult with a grey-flecked coat. Coat colour alone does not show age; many young guinea pigs are born with roan or grey-ticked fur.

How to tell a guinea pig’s age

You cannot pin down an adult guinea pig’s exact age. Size and weight give a good estimate up to about 1 year, and after that you can only tell a young adult from an old one. Guinea pig teeth grow throughout life, so a vet cannot age them by the teeth as with horses.

• Weight and size. A pup weighs 100 to 120 g at birth. A guinea pig that is still clearly growing is under a year old; one at a steady adult weight of about 1 kg (0.9 to 1.2 kg for most) is at least 8 to 12 months.
• Body shape. Pups and juveniles have short faces, small bodies and large heads for their size. Adults are longer and heavier through the hips.
• Teeth. All 20 teeth grow continuously and are worn down by chewing hay. White, even incisors are normal at any age. Overgrown or uneven teeth point to a diet or dental problem, not to age.
• Coat. A young guinea pig’s coat is soft and full. Thinning fur and reduced grooming are common signs of ageing (Vet Verified).
• Eyes. Bright, clear eyes are normal at every age. Cloudy eyes are a common sign of ageing and can mean cataracts; have a vet check them.
• Nails. Nails grow at every age and need trimming every few weeks (MSD). Long, thick or curled nails show missed trims, which can happen at any age. Overgrown nails were the most common disorder in UK guinea pigs, at 26.6% (O’Neill et al. 2024).
• Behaviour. Young guinea pigs “popcorn” (jump and twist in the air) and run more. Older ones sleep more, move more stiffly and are less active.

Signs of a young guinea pig: still gaining weight, small size, short face, frequent popcorning. Signs of an older guinea pig: stable or falling weight, thinning coat, cloudy eyes, stiffness, more sleep. If you adopt a guinea pig of unknown age, a vet can estimate whether it is a juvenile, an adult or a senior, and the calculator works with that estimate.

Guinea pig breeds and lifespan

No study has shown that breed changes how long a guinea pig lives. Mata (2025) compared 47 pure-bred and 627 domestic guinea pigs and found no difference in survival. The sample was small, but it is the only test that exists. In UK vet care, 97% of guinea pigs have no breed recorded at all (O’Neill et al. 2024), and adult body weight is about the same across breeds, which differ mainly in their coats.

Breed sites still give a lifespan for each breed. The table below lists them as published, with the calculator’s figure next to them. The calculator uses 6 years for every breed.

The breed figures come from one breed-site table (Hepper), which follows a PetMD claim that hairless guinea pigs live 7 to 8 years and long-haired ones about 4. Neither source cites data. Applying those ranges would make a 4-year-old Texel 49 in human years and a 4-year-old Peruvian 65, 16 years apart with no evidence behind the gap.

Skinny pig lifespan and care

A skinny pig is a hairless guinea pig with fur only on its muzzle and feet, and it lives about as long as any other guinea pig. Published figures conflict: PetMD and Hepper say 7 to 8 years, Wikipedia gives 5 to 7, and A-Z Animals says hairless guinea pigs may live shorter lives. None of them cites survival data, and only 10 skinny pigs appeared in the 51,622 UK vet records. The calculator uses 6 years.

Without fur a skinny pig loses heat faster, so it eats more than a furred guinea pig and needs a steady, warm room, soft bedding and a cage out of direct sun (Hepper; A-Z Animals). Its skin scratches, dries and burns easily. The Baldwin is a second hairless breed; Baldwin pups are born with fur and lose it within weeks.

Abyssinian guinea pig lifespan

Abyssinian guinea pigs live about 5 to 8 years by breed-site figures, the same range as guinea pigs in general. The Abyssinian has a short, rough coat that grows in whorls called rosettes, usually 6 to 8 of them (Hepper). It is the most often recorded named breed in UK vet practices, at 661 of 51,622 guinea pigs. Weekly brushing keeps the rosettes free of tangles and loose hay. Satin Abyssinians have been linked to a bone disorder (osteodystrophy), according to Hepper; this has not been confirmed in a published study.

Peruvian guinea pig lifespan

Peruvian guinea pigs live about 4 to 6 years by breed-site figures, though no data show that long-haired guinea pigs die younger. The Peruvian’s straight coat can grow to the floor and covers the face. It mats, traps urine and droppings and hides weight loss, so it needs daily brushing and regular trims around the rear. The Silkie, Coronet, Texel, Alpaca, Merino and Lunkarya are the other long-haired breeds; the Texel’s long curls are prone to rubbing the eyes (trichiasis).

Teddy guinea pig lifespan

Teddy guinea pigs live about 4 to 8 years by breed-site figures. The Teddy has a short, dense, wiry coat that stands up from the body, and it is the second most recorded named breed in UK vet records (135). The coat needs little grooming, though a weekly brush and a look at the skin underneath catch hay, dirt and parasites early. The Rex has a similar coat, and the Swiss Teddy, a Rex and Teddy cross, has a denser, wavier one.

How to help a guinea pig live longer

Most guinea pigs that die young die of preventable or treatable problems, and many of them start with not eating. In the VetCompass data the most common recorded causes of death were anorexia (13.9%), collapse (9.8%) and death during anaesthesia (3.4%). Grouped by body system, appetite disorders led (14.2%), followed by lower respiratory disease (10.7%) and collapse (10.2%).

• Vitamin C every day. Guinea pigs cannot make vitamin C because of a gene mutation, and they store it only briefly (MSD; RSPCA). A lack of it weakens collagen in joints, gums and the tissue that anchors teeth. Feed fresh vegetables daily, such as bell pepper and leafy greens, and a guinea pig pellet with stabilised vitamin C. Rabbit pellets and old pellets do not supply enough.
• Unlimited hay. Grass hay should make up most of the diet. Chewing it wears down the teeth, which grow all the time, and keeps the gut moving. Too little hay is one cause of overgrown teeth (MSD).
• Check teeth and appetite. Drooling, dropping food, weight loss or eating less can mean dental disease. A guinea pig that stops eating for even a day needs a vet, because anorexia was the leading recorded cause of death.
• Weigh weekly. Weight loss is often the first sign of illness, and in UK records it was the disorder seen at the oldest median age, 4.64 years. A kitchen scale and a notebook are enough.
• Keep at least two. Guinea pigs are social and the RSPCA advises against keeping one alone. Two sows, two neutered or sibling boars, or a neutered boar with a sow all work (Blue Cross). No study has measured whether pairs live longer; the case for company is welfare, not lifespan data.
• Trim nails and check feet. Overgrown nails were the most common problem in UK guinea pigs under vet care. Trim every few weeks and use solid, soft flooring to protect the feet.
• See a vet that treats guinea pigs. Book a yearly check for adults and one every 6 months from age 4. Guinea pigs hide illness, so a quiet, hunched or fluffed-up guinea pig should be seen the same day.
• Do not breed. Difficult births are a risk, and caesarean sections have a poor survival rate for the mother (MSD).

For more on how guinea pigs fit among their relatives, see the characteristics of rodents and the list of rodent examples.

Oldest guinea pig on record

The oldest guinea pig on record is Snowball, who died on 14 February 1979 at 14 years 10.5 months. Snowball belonged to M. A. Wall of Nottinghamshire, UK, and still holds the Guinness World Records title (Guinness, oldest guinea pig ever).

Other claims, including a Grimsby guinea pig called Bear at 13 to 14 years, were never verified. The calculator reaches its 122 cap at 14.88 years, the age of Snowball’s record.

Other pet age calculators

The same method converts other pets’ ages. The dog years calculator works by breed and size, the cat years calculator by breed, and the horse years calculator covers horses, ponies, donkeys and mules. All of them are on the calculators page.

How this calculator works

The calculator pairs four developmental milestones with human ages, runs a straight line from age 1 to the typical lifespan of 6 years, then slows down to reach 122 at the record age.

The model

1. Fixed anchors. Birth is 0. At 3 weeks a guinea pig is 3 in human years: weaning, paired with the end of human infancy because guinea pig pups are born furred, with open eyes, and eat solids within days. At 2 months it is 12, sexual maturity (MSD gives 2 months for sows and 3 for boars). At 6 months it is 18, about full size, with growth plates closing, matched to the end of human long-bone growth. At 12 months it is 24, adult weight (Witkowska et al. 2014).
2. Linear to the typical lifespan. From 1 year to 6 years each guinea pig year adds 11 human years (0.917 per month), so a 6-year-old reads 79, US life expectancy at birth (CDC NCHS Data Brief 548). The pace just before age 1 is 1.0 human year per month, so the line has almost no kink at the join.
3. A slower tail. Past 6 years each guinea pig year counts 0.44 of an earlier one, 4.84 human years. That factor makes Snowball’s 14 years 10.5 months land on 122, the oldest verified human age. The result is capped at 122.
4. One scale for every breed and both sexes. Breed and coat type select care notes only. No study has found a breed effect, and the two analyses of sex disagree.

Why 6 years

The typical lifespan is the number that sets the adult pace. The measured median, 4 years, would make a 4-year-old guinea pig 79 and a 5-year-old about 90, which clashes with vets and charities who call 4 the start of the senior stage and quote 5 to 8 years (MSD), 5 to 6 (RSPCA, VCA) and 4 to 8 (Blue Cross, Guinness). Six is the middle of those ranges and the same “well-kept pet” choice used in the horse calculator. The cost is that only about 1 in 6 UK guinea pigs in vet care reach 6, so a 5-year-old reading 68 is older, relative to its peers, than a 68-year-old person.

Validation

• The human age rises with every month of guinea pig age from 0 to 15 years, and the human-to-guinea-pig conversion is the exact inverse.
• Checks against the records: AnAge’s 12-year maximum reads 108.0, the owner-survey 13 years 112.9 and the VetCompass 10 years 98.4.

Limitations

• No measurement defines a guinea pig’s “human age”. Every conversion, including this one, is a model.
• The human values for the anchors (3, 12, 18 and 24) are modelling choices matched to guinea pig milestones. The milestones are sourced; the pairings are judgments.
• The only survival data come from UK vet records in a single year. No cohort exists for the US or elsewhere.
• The 6-month anchor rests on a 1938 study of growth plates (Zuck) that we could read only through a summary.
• Sows mature about a month earlier than boars. A sex setting would change results by 1 to 3 human years between 3 weeks and 3 months, so the calculator does not offer one.
• No DNA-methylation clock has been published for guinea pigs, so unlike the dog calculator there is no epigenetic comparison.

Sources

• O’Neill DG, Taffinder J, Brodbelt DC, Baldrey V (2024). Demography, commonly diagnosed disorders and mortality of guinea pigs under primary veterinary care in the UK in 2019: a VetCompass study. PLOS ONE 19(3):e0299464. doi:10.1371/journal.pone.0299464
• Mata F (2025). Cavy lifespan: survival analysis and lifetables for the pet guinea pig (Cavia porcellus) in Britain. PeerJ 13:e19702. doi:10.7717/peerj.19702
• Witkowska A et al. (2014). Computed tomography analysis of guinea pig bone: architecture, bone thickness and dimensions throughout development. PeerJ 2:e615. doi:10.7717/peerj.615
• Vieu S et al. (2024). Assessing pubic symphysis evolution in guinea pigs (Cavia porcellus). Veterinary Medicine and Science 10(6):e70076. doi:10.1002/vms3.70076
• Trillmich F, Laurien-Kehnen C, Adrian A, Linke S (2006). Journal of Zoology 268:285-294 (age at puberty in cavies).
• Harrup AJ, Rooney N (2020). Current welfare state of pet guinea pigs in the UK. Veterinary Record 186(9):282. doi:10.1136/vr.105632
• MSD Veterinary Manual: description and physical characteristics, physiological data, biological data of pet rodents, routine care, common health problems, breeding and reproduction.
• RSPCA, guinea pigs; Blue Cross, guinea pig care; VCA, owning guinea pigs; PetMD, how long do guinea pigs live; Vet Verified, caring for an ageing guinea pig.
• Hepper, guinea pig breeds (breed lifespans); Wikipedia, Skinny pig.
• Guinness World Records. Oldest guinea pig ever. AnAge: Cavia porcellus.
• Omni Calculator. Guinea pig age calculator (the popular chart).
• NCHS (2026). Mortality in the United States, 2024. Data Brief 548 (US life expectancy 79.0 years).

The breed lifespans, all conversions and the charts are florafaunafun.com calculations, and the original authors did not review or endorse them.

How old is a 1-year-old guinea pig in human years?

A 1-year-old guinea pig is about 24 in human years, a young adult. Guinea pigs are weaned at 3 weeks, can breed at 2 months and reach adult weight at 8 to 12 months, so they cover the human childhood and teenage years in their first year. A 2-year-old is 35 and a 4-year-old is 57.

How long do guinea pigs live?

Pet guinea pigs live 5 to 8 years with good care, and the median age at death in UK vet records is about 4 years. The 4-year median comes from 674 deaths in the VetCompass study (O'Neill et al. 2024); in the same data about 1 in 3 guinea pigs reached 5 and 1 in 6 reached 6. Vets and charities quote 5 to 8 years (MSD), 5 to 6 (RSPCA) and 4 to 8 (Blue Cross).

What age is a senior guinea pig?

A guinea pig is a senior from about 4 years old, which is 57 in human years. PetMD puts the senior stage at 4 and UK vet guides at 4 to 5, and the calculator calls a guinea pig geriatric from 5 (human 68). Book vet checks every 6 months from age 4.

How can you tell how old a guinea pig is?

You can estimate a guinea pig's age from its size and weight up to about 1 year, but not the exact age of an adult. A guinea pig that is still growing is under a year old, and one at a steady adult weight of about 1 kg is at least 8 to 12 months. Older guinea pigs sleep more, move more stiffly and may have thinning fur or cloudy eyes; the teeth grow all their life and do not show age.

When is a guinea pig full grown?

A guinea pig is close to full size at about 6 months and reaches its adult weight at 8 to 12 months. A CT study found that the skeleton keeps developing after the first year (Witkowska et al. 2014). Adult guinea pigs in UK vet records weigh a median 1.05 kg.

How long do skinny pigs live?

Skinny pigs live about as long as other guinea pigs, around 5 to 8 years with good care. Published figures conflict (PetMD 7 to 8 years, Wikipedia 5 to 7) and none is based on survival data, so the calculator uses the same 6-year lifespan as every other breed. Hairless guinea pigs need a warm room, soft bedding and more food to stay warm.

Do guinea pigs live longer in pairs?

No study has measured whether guinea pigs live longer in pairs, but they should not be kept alone. Guinea pigs are social animals, and the RSPCA and Blue Cross both advise keeping at least two. The reason is welfare: a lone guinea pig lacks the company it needs.

What is the oldest guinea pig ever?

The oldest guinea pig on record is Snowball, who died in Nottinghamshire, UK, on 14 February 1979 at 14 years 10.5 months. Guinness World Records still lists Snowball as the record holder. That age equals 122 on this calculator, the oldest verified human age.

Is 1 guinea pig year equal to 12 human years?

No, a 1-year-old guinea pig is about 24 in human years, not 12. Times 12 makes a 2-month-old guinea pig 2, at an age when it can already breed, and it ignores how fast guinea pigs grow in their first year. The popular online chart errs the other way, putting a 5-year-old at 140.

How accurate is the guinea pig years calculator?

The calculator gives a reasoned estimate, not a measurement, because no biological test defines a guinea pig's human age. Its first-year values are tied to measured milestones (weaning, sexual maturity, adult size and weight) and its adult pace makes a 6-year-old guinea pig 79, US life expectancy. It is less certain past age 6, where it is tied to the record age of 14 years 10.5 months.