About This Site
Most puppy weight calculators do the same two things: they hide which formula they are using, and they print one confident number. For a growing animal, that number is fiction. This site shows both methods it uses, names their assumptions, marks where each stops being valid, and always answers with a range.
It is built and maintained by an independent developer who makes small, focused web tools. It is not run by a veterinary practice or a breeder, and nothing here is veterinary advice.
The two methods
- Growth-fraction method. Puppies reach a roughly predictable percentage of adult weight at each age, and that percentage depends strongly on adult size class. Divide the current weight by the fraction for the puppy's age and class and you get an adult estimate. Our per-size fraction table is an approximation compiled from commonly published veterinary and breeder growth guides, rounded to whole percentage points, and every estimate derived from it carries a ±15% band. It is published in full on the puppy growth chart.
- Simple linear rule. (current weight ÷ age in weeks) × 52. A widely circulated shortcut that assumes constant growth ending at exactly one year. Both assumptions are wrong: growth is front-loaded, so it overshoots for early-maturing toy breeds, and it is least accurate for large and giant breeds that are nowhere near finished at 52 weeks. We show it because you will meet it everywhere and comparing it against the fraction method is genuinely instructive — but we stop folding it into the headline range past 26 weeks and stop showing it past 52.
Accuracy rules
- No invented precision. The output is always a range. Values are rounded to one decimal below 10 units and to whole numbers above, because neither method supports more.
- No fabricated breed curves. We do not publish per-breed growth data we have not got. The breed pages take a published breed-standard adult range and multiply it by the size-class fractions — and say so on the page.
- Every method is labelled wherever a number appears, along with what it assumes.
- Honest failure modes. Where a rule stops meaning anything, we remove it instead of quietly printing something plausible.
- No health claims. Growth-stage labels are descriptive conventions, not diagnoses.
What the tool cannot do
It cannot tell you whether your puppy is healthy, whether it is growing correctly, or what it should weigh today. Those are questions about one specific animal, and they belong to a veterinarian who can examine it. A calculator that implies you should feed a puppy toward a chart is giving harmful advice; growth curves are for planning crate sizes and budgets, not for setting targets.
Your data
Everything runs in your browser. There is no account, no server-side computation, and no logging of the values you type — the weight and age you enter never leave your device. Details are in the privacy policy.
Related tools
We also build the Dog Age Calculator, which converts dog years to human years under the same rules: two labelled methods, no fake precision.
Corrections
If you find an arithmetic error, a mis-stated method, or a claim that overreaches the evidence, please say so — corrections get made. Use the contact page.