How big will my puppy get? What real growth data shows

The short answer: weight, age and size class

Puppies don’t grow in a straight line. They put on weight fast in the first few months, then slow down and level off, and small dogs level off sooner than big ones. So the useful question is not how many pounds a week a puppy gains, but what share of its adult weight a puppy like yours has reached by now.

Once you know that share, the estimate is one division: today’s weight divided by the share. The share depends on three things:

• Age in weeks. At 12 weeks a puppy is a much smaller fraction of its adult self than at 26 weeks.
• Size class. A toy dog is half grown by about 16 weeks; a giant dog is not.
• Where your puppy sits among its peers. Some puppies are early growers and some are late ones, which is why every estimate is a range.

This is general information, not veterinary advice — talk to your vet about your own puppy’s growth and body condition.

Why size class matters

The 2017 study grouped breeds by the average adult weight of that breed in its database, and its authors noted that no standard size grouping exists for dogs. We use the same six classes, by expected adult weight:

Two details matter here. First, the class comes from the breed the paper names, not from a breed standard: Shih Tzus and Dachshunds sit in class II because that is where the study placed them. Second, the 2017 standards stop at 40 kg; the authors say they do not apply to dogs heavier than that. Our class VI numbers come from the same raw data and are labeled less predictable for that reason.

If you don’t know the breed, the class can come from the parents’ adult weights or from your puppy’s own weight and age — see the guide to mixed-breed puppies, listed below.

How much of adult weight a puppy has at each age

Here is the typical (median) share of adult weight by age for each class, from our summary of the study data. “Adult weight” in this data is the same dog’s median weight at 2 to 3 years old, so it includes the small gain many dogs make in early adulthood.

Read across a row and you see the curve: fast early growth, then a long, slow finish. Read down a column and you see why one rule can’t fit every dog. At 16 weeks a toy puppy is typically at half its adult weight, while a giant puppy is at about a third.

These are medians. Half of the puppies in each cell were further along and half were behind, which is where the ranges in the next sections come from.

A worked example: a 25-lb Labrador at 16 weeks

Take a male Labrador Retriever puppy who weighs 25 lb (11.3 kg) at 16 weeks. The study places Labradors in class V.

1. Share reached. A typical class V puppy at 16 weeks has reached 41% of its adult weight.
2. Central estimate. 25 lb divided by that share gives about 61 lb (27.9 kg).
3. Middle half. Using the 25th and 75th percentiles of the share instead of the median gives 55 to 69 lb (25.0–31.4 kg). Half of puppies like this one ended inside that band.
4. Wider band. Using the 10th and 90th percentiles gives 51 to 79 lb (22.9–35.9 kg). About 8 in 10 ended inside it.

Notice how much the age matters. The same 25 lb points to very different adults depending on when it is reached: about 91 lb at 12 weeks, 61 lb at 16 weeks, 47 lb at 20 weeks and 36 lb at 26 weeks. A mistake of a few weeks in the age moves the estimate more than most owners expect, so use the real birth date if you have it.

Why the range is wide — and wider for toy dogs

A range of 55 to 69 lb can feel unhelpful, but it is the honest width. Puppies of the same breed, sex and weight really do end up at different adult weights, and no calculator can know which kind of puppy yours is from one weigh-in.

The width is not the same everywhere. For toy breeds, the sources also disagree with each other:

• In our summary of the 2017 data, a class I puppy at 12 weeks has typically reached 39% of adult weight, and the middle half of puppies sat between 32% and 45%.
• A 2004 study by Hawthorne and colleagues weighed 173 kennel puppies of 12 breeds every week and fitted a growth curve to each breed. Working its published curve for Papillons forward to 12 weeks gives about 53% — far ahead of the pet data. That curve rests on three Papillons.

For Labradors the two sources agree closely: the 2004 curve gives about 41% at 16 weeks, the same as class V in the pet data. The two also define “adult” differently: the 2004 study measured to the plateau of each breed’s curve, while our tables use each dog’s own weight at 2 to 3 years. A later, heavier adult weight makes every share a little smaller and every estimate a little higher.

What this means in practice: a 1.5-lb Chihuahua at 12 weeks has a central estimate of 3.9 lb as an adult, with a middle half of 3.3 to 4.7 lb and an 8-in-10 band of 2.9 to 5.6 lb. For a toy dog, a pound either way is a big share of the animal, so treat early toy estimates loosely and weigh again.

Sex and neutering. Our share-of-adult tables pool males and females, so a 25-lb female Labrador at 16 weeks gets the same central estimate, 61 lb, as the male in the example: the study places Labradors in class V for both sexes. The centile lines on the growth chart are drawn separately for each sex, because the weights behind them differ. Neutering mattered less than you might think: the 2017 authors found that the shifts after neutering were small compared with the differences between individual dogs, and they did not build separate charts for neutered dogs.

Giant breeds are less predictable too. A male Great Dane weighing 65 lb at 20 weeks has a central estimate of 135 lb, but the middle half runs from 124 to 150 lb and the 8-in-10 band from 115 to 172 lb.

Why calculators disagree

If you have tried three calculators and got three answers, here is usually why.

A straight-line formula. Some tools divide today’s weight by the age in weeks and multiply by 52, as if puppies gained the same amount every week for a year. Growth is not a straight line, so this overshoots. For the typical toy or small puppy it runs 43% to 67% too high between 12 weeks and 6 months; for large breeds about 20% to 37% too high. Our 1.5-lb Chihuahua would be forecast at 6.5 lb, and the 25-lb Labrador at 81 lb.

A single doubling rule. Doubling the weight at 16 weeks is right on average for toy dogs (0% median error) but runs 19% low for class V puppies and 29% low for giants. Even where the median is right, only 35% of toy puppies land within 10% of their real adult weight. The guide to puppy weight rules of thumb tests six of these rules size by size.

Breed-standard weights. A tool that looks up a breed’s standard range is giving you the breed, not your dog. A 2023 study of about 115,000 young adult dogs of 72 breeds notes that weight can vary considerably within a breed, and that breed standards, often written as ranges or maximums, may not be valid references.

The wrong size class. Picking a class one step off moves the estimate, but less than people fear in the middle sizes: the same 25 lb at 16 weeks gives 60 lb as class IV and 61 lb as class V. It matters more at the edges, especially between toy and small and between large and giant.

When growth ends

In the study data, the typical puppy reaches 90% of its adult weight at about 10½ to 14 months and 95% at about 16½ to 20 months, depending on the class. The large class V reaches 90% at 46 weeks (about 10½ months) and 95% at 72 weeks (about 16½ months).

The Merck Veterinary Manual gives 8 to 12 months for growth and skeletal maturity in small and medium breeds and 10 to 16 months in large and giant breeds. The 2004 kennel study put 99% of adult weight at about 9 to 10 months for toy to medium breeds and 11 to 15 months for large and giant breeds. The sources measure “done” differently, which is why their numbers differ; the guide on when puppies stop growing puts them side by side.

Our predictions start at 8 weeks, are marked as early estimates before 12 weeks, and stop at about 18 months. By then the typical dog in this data has reached 93% to 95% of its adult weight, and body condition tells you more than any growth table.

Estimate it yourself, step by step

You can do this by hand, or let the puppy weight calculator do the arithmetic.

1. Weigh accurately. Use the same scale each time, at about the same time of day, before a meal. Small puppies are easier on a kitchen or baby scale; larger ones can be weighed by holding them on a bathroom scale and subtracting your own weight.
2. Work out the exact age in weeks. Count from the birth date (day 0) to the day of the weigh-in and divide by 7. If nobody knows the birth date, ask your vet for an estimate of the age.
3. Pick the size class. Use the breed if the study places it in a class; otherwise use the parents’ adult weights or your puppy’s own weight and age.
4. Find the share reached. Use the table above, reading between columns for ages in between.
5. Divide. Today’s weight divided by the share is the central estimate. Dividing by the 75th and 25th percentile shares gives the middle-half range.
6. Weigh again every 2 to 4 weeks. That is the schedule WALTHAM suggests up to 6 months (then every 1 to 3 months until fully grown). Three or more weigh-ins tell you far more than one.
7. Watch the trend, not one number. If the estimates settle, your puppy is following its curve. If they keep drifting up or down, look at the centile lines and talk to your vet.

Here is how that looks for a male class V puppy weighed four times:

The central estimate wobbles between 66 and 73 lb, and the bands narrow as the puppy gets older. The puppy moved between neighboring bands but ended in the band it started in, so it crossed no centile lines overall and the growth chart would raise no flag.

Centile lines, and when to talk to your vet

A centile line shows the weight below which a given share of healthy puppies of that size, sex and age fall: the 25th line is the weight that a quarter of puppies are under. A puppy who starts near the 50th line and stays near it is growing like the typical puppy; one who starts at the 25th and stays there is simply a smaller dog.

What matters is crossing lines. In a 2020 follow-up study of the growth standards, crossing more than two centile lines during growth was uncommon in healthy dogs: fewer than 5% did. Among dogs that had become obese by 3 years, 68% had crossed two or more lines upward; among dogs that had become underweight by 3 years, 49% had crossed two or more lines downward. The same paper is careful to add that the standard “is not a diagnostic test.” Crossing lines raises the question; your vet answers it, alongside body condition scoring.

Talk to your vet if your puppy:

• crosses two or more centile lines in either direction,
• stops gaining, or loses weight, before it is fully grown,
• sits below the lowest or above the highest line for its class and sex, or
• seems unwell, whatever the scale says.

Your vet can also check body condition, which tells you whether the weight is the right weight for the frame.

Next step

Enter your puppy’s weight, age and breed (or size class) in the puppy weight calculator for the estimate and both ranges, then add each weigh-in to the puppy growth chart to see which centile band your puppy follows. The full tables behind both tools, with downloads, are on the puppy growth standards page.