Guinea Pig Weight Chart: Healthy Weight by Age, Sex & Breed

A guinea pig's weight is one of the clearest windows into her overall health, since guinea pigs are prey animals that instinctively hide signs of illness until a problem is already well underway. A healthy adult female typically weighs somewhere between 700 and 1,100 grams while a healthy adult male usually falls between 900 and 1,500 grams, though breed and individual build shift that range in either direction. This guide breaks down what a guinea pig should weigh at every life stage, how to weigh her correctly at home, and the specific warning signs of weight loss or weight gain that are worth a call to an exotic-animal vet rather than a wait-and-see approach.

Why Guinea Pig Weight Matters More Than It Seems

Guinea pigs are a prey species, and in the wild a visibly weak animal attracts predators, so they keep eating, moving, and grooming as normally as they can for as long as they can. By the time a pig looks unwell, she has often been losing weight for days, which is why the scale picks up trouble before behavior does.

Regular weighing turns a vague sense that something seems different into an actual data point, which is exactly why weekly weigh-ins are considered standard practice among exotic-animal vets rather than an optional extra step.

A weight log also gives your vet a baseline to compare against. Because an adult guinea pig weighs only around a kilogram, a loss of 30 to 50 grams is a meaningful share of her body, and it shows up on a kitchen scale well before it is visible to the eye. Catching a downward trend in the first week or two, rather than the first month, makes a real difference to how quickly a cause is found.

Guinea Pig Weight Chart by Age

Growth happens quickly in the first few months of life and then levels off as a guinea pig reaches maturity. The ranges below reflect general growth patterns reported across guinea pig care resources and should be read as a normal window rather than an exact target.

• At birth: roughly 85 to 100 grams (about 3 to 3.5 ounces)
• 2 months old: roughly 180 to 240 grams
• 3 months old: roughly 240 to 360 grams
• 6 months old: roughly 500 to 900 grams depending on sex and build
• 12 to 14 months old (adult): growth typically plateaus around this age

Growth Slows Once a Guinea Pig Reaches Adulthood

Most guinea pigs reach their adult size at around 12 to 14 months, although weight can keep drifting afterward with diet, activity, and age. Once growth has levelled off, her weigh-ins should sit within a few percent of one another, so a sudden shift in either direction stands out.

Weight Gain in the First Weeks of Life

The fastest growth happens in the first eight weeks, which is also the window where a daily or every-other-day weigh-in matters more than the weekly schedule used for adults.

• Day 1: roughly 85 to 100 grams at birth, with pups from larger litters typically starting nearer the lower end
• 1 week old: a small but steady gain most days is expected, and a pup that isn't gaining at all in the first week is worth mentioning to a vet
• 3 to 4 weeks old: usually well past 200 grams, and this is also the general window many breeders use for weaning
• 6 to 8 weeks old: approaching or within the 2-month range noted above as growth continues at a steady pace

A newborn who loses weight in the first 48 hours rather than holding steady or gaining, or who feels notably lighter than her littermates, is worth a same-day call to an exotic-animal vet rather than a wait-and-see approach.

Healthy Adult Weight by Sex and Breed

Sex is the biggest single factor separating one healthy adult weight from another, with build and breed adding some additional variation on top of that baseline.

Female Guinea Pigs

Most sources place a healthy adult female's weight between 700 and 1,100 grams, or roughly 1.5 to 2.5 pounds. A female who has been pregnant may temporarily weigh more during and shortly after that time before settling back toward her usual range.

Male Guinea Pigs

Adult males generally run larger, typically falling between 900 and 1,500 grams or about 2 to 3.5 pounds. The wider range reflects how much build and breed can influence a male's healthy weight compared to females.

Breed and Individual Variation

A guinea pig's healthy weight isn't a single fixed number even within the same sex, since breed, bone structure, and individual build all play a role. A guinea pig who sits slightly above or below the typical range but has consistently stayed there, eats normally, and has a visible waist is usually not a cause for concern on weight alone.

How to Weigh Your Guinea Pig Correctly

A digital kitchen food scale accurate to a few grams works far better than a bathroom scale, which isn't sensitive enough to catch meaningful changes in an animal this small.

Weighing Tips

• Place a small bowl or container on the scale and zero it out before adding the guinea pig
• Weigh on the same day and at about the same time each week, because a pig that has just eaten a large meal or been drinking can read a little heavier than one weighed at a different time of day
• Keep her still for a few seconds by offering a small piece of vegetable while the scale settles
• Record the number in grams straight away, along with the date, so you are comparing like with like from week to week

How Often to Weigh

Most exotic-animal vets suggest a weekly weigh-in for a healthy adult, on the same day and ideally at the same time. Pups, pregnant sows, and any pig recovering from illness are better weighed every day or two. One number on its own says little; what matters is how this week compares with the last several.

Is Your Guinea Pig Underweight or Overweight?

The scale is only half of the picture, because two guinea pigs of the same weight can be built very differently. A long, large-framed boar and a compact sow may both be healthy at weights that would be too high or too low for the other, so judge weight together with how she looks and feels.

Signs of Being Underweight

• Ribs, spine, or hip bones that feel sharp and prominent rather than lightly padded
• A visible dip or hollow around the hips and lower back
• Reduced energy or a noticeable drop in normal activity
• A steady downward trend across multiple weekly weigh-ins

Signs of Being Overweight

• No visible waist when viewed from above
• Ribs that are difficult to feel under a thick layer of fat
• Fat rolls or pads around the neck, shoulders, or hindquarters
• Difficulty reaching the belly or hindquarters during normal grooming

While she is on the scale, run a hand lightly along her back and sides. A healthy pig feels firm and rounded, with ribs you can find under a thin cushion of padding; a pig whose spine feels like a ridge is too thin, and one whose ribs you cannot find is too heavy.

When Weight Loss Is an Emergency

A guinea pig that is losing weight is rarely just thin. Her gut depends on a steady stream of fiber, so even a short stretch of poor eating can slow digestion further and make her eat less still. That is why weight loss in this species is treated as urgent rather than something to monitor for a month.

Common Causes of Weight Loss

dental disease causing painful chewing is one of the most common underlying causes, since overgrown or misaligned teeth make chewing painful enough that a guinea pig quietly eats less without any other obvious sign. Reduced appetite from stress, digestive upset, parasites, infection, or organ disease can all drive weight loss as well, and more than one cause can be at play at the same time.

• Dental disease: guinea pig teeth grow continuously, so overgrown or misaligned molars and incisors make hay painful to chew and eating slows gradually
• Vitamin C deficiency: guinea pigs cannot make their own vitamin C, and a shortage leads to scurvy, which shows up as lethargy, poor appetite, weight loss, a rough coat, and sore joints
• Gastrointestinal stasis: slowed gut movement, usually seen as small or absent droppings together with refusing food, and it can become life-threatening within a day or two
• Respiratory infection: often paired with sneezing, noisy breathing, or discharge from the eyes or nose alongside a drop in appetite and weight
• Mites and other parasites: heavy mite burdens cause intense itching and scratching, and the stress and discomfort can pull body condition down over weeks
• Bladder stones or urinary disease: common in guinea pigs and often accompanied by straining, squeaking when urinating, or blood in the urine
• Social or environmental stress: a new cagemate, a move, or a loud room can suppress appetite temporarily in an otherwise healthy pig

How Much Weight Loss Is Too Much

For an animal that weighs around a kilogram, a loss of 50 grams is about 5 percent of her body weight in a single week. Call an exotic-animal vet if a pig has lost weight across two weigh-ins in a row, and the same day if the drop comes with eating less, smaller droppings, hunching, or drooling. a sudden drop in appetite alongside a drop in weight is an especially strong signal that something needs veterinary attention soon, since the two together often point to the same underlying cause.

Weighing Guinea Pigs in Multi-Pig Households

Guinea pigs are herd animals and generally do better with a companion, but a shared enclosure makes it hard to see which pig is eating less. A bonded pair can look equally well fed from the doorway while one of them is slowly losing ground.

Tips for Multi-Pig Weigh-Ins

• Weigh every pig on the same day and keep a separate log for each, because an unchanged average can hide one pig declining while another gains
• Offer more than one hay rack and food bowl, placed apart, so a dominant pig cannot guard the only supply
• Watch for a pig that eats only when her cagemate is out of the way, since that is often an early sign that she is not getting her share
• If one pig starts to slip, feed her separately for a few days and see whether her weight recovers, which helps tell competition apart from illness
• Weigh pups and their mother separately, since a nursing sow can lose weight while her litter gains

Guinea Pig Obesity: Risks and Prevention

Guinea pigs gain weight gradually, which makes it easy to miss until the extra weight is already causing problems. Unlimited pellets, a daily helping of sweet vegetables and fruit, and little room to run are the usual combination.

Health Risks of Excess Weight

Extra weight presses on the soles of the feet, which raises the risk of bumblefoot (pododermatitis), a painful sore that is hard to treat. It also strains the heart and joints and makes it harder for a pig to reach and clean her rear end. Overweight sows are also more prone to pregnancy toxemia, a serious condition late in pregnancy, so breeding or accidental pregnancy in an obese sow is a particular concern.

Preventing Unhealthy Weight Gain

Unlimited grass hay should make up most of her diet, with a measured portion of plain pellets and a modest helping of vegetables rather than free-fed pellets or a bowl of fruit. Treats high in sugar, such as carrots, apple, and dried fruit, are best kept occasional. Daily time outside the cage matters too, and daily supervised floor time gives her room to move around and stay active rather than sitting in one spot most of the day.

Expert Tips for Tracking Guinea Pig Weight

• Use grams rather than ounces, since a change of 20 or 30 grams is easy to see in grams and easy to round away in ounces.
• Take a photo of her from above every month so changes in shape are easier to compare than they are from memory.
• Keep the scale and a small box or bowl in the same place so weighing becomes a calm routine instead of a chase.
• Bring the log to every vet visit, since a documented trend helps narrow down a cause much faster than a single weigh-in.
• Expect a sow's weight to rise during pregnancy and fall after birth, and a pig's weight to dip slightly while she moults, rather than assuming every change is a problem.

Common Mistakes to Avoid

• Weighing only when something already seems wrong, which leaves no baseline to compare against
• Assuming a thin pig is just built that way without checking that her weight has actually been stable
• Free-feeding pellets and sweet treats, which fills her up and displaces the hay her teeth and gut need
• Judging her against an online average instead of her own steady weight
• Waiting to see whether a weight drop corrects itself before calling a vet

Final Thoughts

A healthy guinea pig weight is less a universal number than a stable personal baseline, generally somewhere between 700 and 1,100 grams for adult females and 900 and 1,500 grams for adult males. A weekly weigh-in together with a quick feel along her back turns a vague worry into real information, and treating a sudden drop or a steady decline as a same-day call to the vet gives her the best chance if something is wrong.

For the everyday habits that keep her weight steady beyond the scale, this complete guinea pig care guide covers housing, diet, and health checks in one place.

Weigh your guinea pig weekly in grams and compare each reading with her own recent numbers, not with an average.

This guide is for general education and is not a substitute for veterinary care. Any guinea pig showing sudden weight loss, a steady downward trend, or signs of obesity-related discomfort should be seen by an exotic-animal veterinarian.