Puppy weight predictor

What it does

Enter a puppy's weight at about four months old, pick the size group you expect, and the tool gives a rough range for its adult weight. If you name a breed, it shows the breed's typical adult range from the breed profile beside the estimate.

How the numbers are worked out

By four months, or 16 weeks, a puppy has reached a share of its adult weight, and that share is smaller for larger breeds. This tool uses a wide band for each size group: roughly 55 to 70 percent for toy and small dogs, 45 to 52 percent for medium dogs, 33 to 47 percent for large dogs and 28 to 38 percent for giant dogs. The puppy's weight is divided by the top and bottom of the band to give the low and high ends of the range.

The bands are deliberately wide because published rules of thumb disagree with one another, and there is no standard growth chart for all dogs. The result is a range to help you plan, not a prediction.

Where it stops being right

Mixed-breed puppies are the hardest to estimate, and the size of both parents is usually the best guide. Growth also depends on food, health and the line a puppy comes from, and a puppy that is a little heavy or light at four months can end up anywhere in the range. A puppy that looks very different from the range, or stops gaining weight, is a reason to ask your veterinarian.

Puppies are not fully grown for a long time. Small breeds usually finish growing at about a year, while large and giant breeds can keep growing for 18 to 24 months. Feed a growing large-breed puppy a food made for it, and do not push it to grow faster.