Skip to content
Omnikalc

Puppy weight calculator: how big will my puppy get?

Estimate your puppy's adult weight from its current weight, age and breed size, with the expected weight at 6 and 12 months.

Updated on
Your inputs

Value out of range

weeks

Value out of range

Results

Estimated adult weight

70 lb

Share of adult weight reached

43%

Expected weight at 6 months
42 lb
Expected weight at 12 months
59 lb
Typical age at adult size
16 months

How the estimate works

Puppies grow fast at first, then slow down as they approach adult size. A simple way to model this is a growth curve where the share of adult weight reached at age t (in weeks) is:

share = 1 − e^(−k × t)

The rate k depends on breed size, because small dogs mature much faster than giants. The adult weight estimate is then current weight ÷ share.

Breed size Typical adult weight Share reached at 16 weeks Adult size at about
Toy or small under 20 lb about 64% 10 months
Medium 20 to 50 lb about 52% 13 months
Large 50 to 100 lb about 43% 16 months
Giant over 100 lb about 35% 21 months

Worked example

Your large-breed puppy weighs 30 lb at 16 weeks.

  1. Share of adult weight reached: about 43%.
  2. Estimated adult weight: 30 ÷ 0.43 ≈ 70 lb.
  3. Expected weight at 6 months: about 42 lb.
  4. Expected weight at 12 months: about 59 lb.
  5. Most large breeds reach adult size around 16 months.

How reliable is it?

Treat the result as a range of about ±15%. The best predictors of adult size are still:

  • The parents’ weights, especially for mixed breeds when you know them.
  • The breed standard for purebred dogs.
  • A DNA test, which can suggest the breeds involved and their usual size.

Growth spurts, illness, diet and neutering age all change the curve. Weighing your puppy every two weeks and rerunning the estimate gives a better picture than a single reading.

Healthy growth

  • Feed a puppy food matched to the expected adult size. Large and giant breeds need large-breed formulas with controlled calcium and energy.
  • Keep puppies lean. You should feel the ribs easily without seeing them. Fast growth from overfeeding raises the risk of hip and elbow dysplasia in big dogs.
  • Adjust portions as your puppy grows, following the food label and your vet’s advice.

This calculator gives general estimates for healthy animals. It does not replace the advice of a veterinarian who has examined your pet.

Frequently asked questions

How can I tell how big my puppy will get?

The most reliable signs are the parents' adult weight and the breed standard. A growth curve based on the puppy's current weight and age gives a useful estimate, and large paws are only a loose hint.

When do puppies stop growing?

Small breeds reach their adult size at about 9 to 12 months, medium breeds at 12 to 15 months, large breeds at 15 to 18 months and giant breeds at 18 to 24 months. They may keep filling out a little afterwards.

Is it true that a puppy doubles its 4-month weight?

For many medium and large breeds, a 16-week-old puppy has reached roughly 40 to 45% of its adult weight, so doubling and adding a bit is a fair rule of thumb. Small breeds are further along at that age and giants are further behind.

How fast should a large-breed puppy grow?

Steadily, not as fast as possible. Large and giant puppies should eat a large-breed puppy food and stay lean, because overfeeding and too much calcium raise the risk of joint and bone problems.

Was this calculator helpful?

Thanks for your feedback!

Results are estimates provided for information purposes. They do not replace professional advice.

Related calculators