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Enter puppy details

Tip: For puppies under 1 year, entering age in weeks is usually easiest.

Height means shoulder height (withers). If you’re not sure, leave this blank.

Even “mix” helps. If we recognize the breed, we blend typical adult ranges with the growth-curve estimate.

If you don’t know size class, we default to Medium unless breed/parent info suggests otherwise.

Options:

Result:

No results yet. Enter values and click Calculate.

How to use this calculator

  • Enter your puppy’s age and current weight (required).
  • Optionally add current shoulder height for a height estimate.
  • Add breed and/or parent sizes for higher confidence.
  • Click Calculate to see predicted adult size ranges.

How this calculator works

  • Convert inputs to consistent internal units (lb/in).
  • Estimate what fraction of adult size is reached at the current age (growth curve).
  • Compute adult size ≈ current size ÷ completion fraction.
  • If available, blend in breed reference ranges and/or parent averages.
  • Return results as ranges with a confidence label (higher with more info).

Formula & Equation Used

Adult weight ≈ Current weight ÷ Weight completion(age, size)

Adult height ≈ Current height ÷ Height completion(age, size)

Parent blending (if provided): Adult size ≈ average(parent sizes) with small adjustments.

Example Problems & Step-by-Step Solutions

Example 1 — Weight-only estimate

A puppy is 12 weeks old and weighs 12 lb.

  1. Convert age to months (≈ 12 ÷ 4.345 ≈ 2.8 months).
  2. Pick a size class (if unknown, default to Medium).
  3. Find completion fraction from growth curve (example: ~0.35 at ~3 months for Medium).
  4. Estimate adult weight: 12 ÷ 0.35 ≈ 34 lb (reported as a range).

Example 2 — Weight + height estimate

A puppy is 20 weeks old, weighs 18 lb, and is 14 in tall (shoulder height).

  1. Convert age to months (≈ 4.6 months).
  2. Estimate adult weight via completion fraction.
  3. Estimate adult height: 14 ÷ heightCompletion(4.6, size).
  4. Return results as ranges.

Example 3 — Using parent sizes

You know the parents’ sizes (even approximate).

  1. Average mom/dad weights for a strong adult weight estimate.
  2. Average mom/dad heights for a strong adult height estimate.
  3. Blend with the growth curve so the result stays realistic.

Frequently Asked Questions

Q: How accurate is this puppy size predictor?

It’s most accurate when you add breed and/or parent stats. Mixes and giant breeds can vary more, so results are shown as ranges.

Q: What height should I measure?

Measure shoulder height (withers): ground → highest point of the shoulders while standing naturally.

Q: Why do you show a range instead of one number?

Dogs vary by genetics, body condition, and growth timing. A range is more honest (and usually more helpful).

Q: Do I need parent information?

No. You can still estimate adult weight from age + current weight. Parent sizes mainly boost confidence and improve height prediction.

Q: What if my puppy is a mix?

That’s totally fine. Enter the main known breed (or “mix”). When breed is unclear, the calculator relies more on age-based growth curves.